The Number 23 is currently in theaters, and as a result, has everyone wondering about the mysterious properties of the number 23.

Yes, there are many unique things about the number 23, but it is far from the only number with such interesting properties. As the Numbers Guy (Carl Bialik) shows, you can find just about as many interesting properties for the number 24, as well.

Are you still not convinced the number 23 is nothing special? Check out What's Special About This Number? and Number Gossip Search/Browse. It's not just whole numbers that have fantastic properties, either, as a trip to Notable Properties of Specific Numbers will prove.

Of course, these sites list numbers with many properties that are interesting mainly to mathematicians. What numbers are interesting to everyday people? You find out at The Secret Lives of Numbers (Java required). This site is the result of a unique project to find the search engine popularity of every number from 1 to 1,000,000. This project ran from December 1997 through January 2002, and provides an interesting view of our world of numbers. For example, you can't find any search engine terms containing 1039, and barely any searches. However, 1040, thanks to being the most prominent US tax form number, returns more terms and far more searches.

Next time, we'll focus on 300 (just kidding).

Philemon Vanderbeck has a new school show called Arithemagic. As you might guess from the name, the focus is on present AND teaching math-based effects.

To get an idea of the show, I suggest checking out the video (play along!) and photo sections.

When performing his school show, Philemon also gives teachers NINE, the lecture notes for the effects taught in the show. These lecture notes are also available for purchase, for $9, of course. As far as the effects themselves go, most of them are classics of mathematical magic, and I've discussed many of them on this site, such as extracting cube roots and fifth roots or the Fibonacci addition trick.

A quick look at the table of contents (PDF) might lead one to think that the notes aren't worth purchasing just because they're classics. However, there are some gems here, such as Werner Miller's Swindle Sudoku, as well as some impressive presentations. NINE has a great presentation for the old 1089 trick. As a matter of fact, NINE and Hidden Numerical Forces are the only two resources I've ever found with engaging presentations for the 1089 trick.

It's great to see math and magic being presented in such a positive and fun way to school students. Teachers and school administrators from Washington state should especially check this site out, but that shouldn't stop others. Anyone interested in mathematical magic should check out this site, as well.

I have good news for the fans of the Carnival of Mathematics! Yes, the 4th Carnival of Mathematics has been posted over at Jason Rosenhouse's EvolutionBlog.

No, you didn't miss the first two reviews. I'm focusing on just one volume of the series, since volume 3 of Sessions With Simon series focuses entirely on magic with a memorized deck.

The “Simon” in the title is none other than Simon Aronson, who is known, among his other talents, as a master of the memorized deck. The video opens with performances of routines which will be familiar to readers of Simon Aronson's books, such as Try The Impossible.

The real meat of the video, however, is in the explanation section. Before the effects are taught, Simon begins with a discussion of the basics of memorized deck work. If you already work with a memorized stack, you may be tempted to skip the basic section, but I think anyone who is interested enough to purchase this video should watch this section at least once. Simon also refers the viewer to even deeper discussion of memorized deck basics in his free online book, Memories Are Made Of This. He discusses the unique nature of the Aronson stack, and what lead to the particular stack order, but he also refers to other stacks. Since he doesn't push the Aronson stack over other stacks, this adds to the value of the DVD as a memorized deck resource.

Next, the effects are taught. Each routine, however, is also an object lesson. Once you've got the deck memorized, a whole host of issues comes up, such as how to get the memorized deck into play without suspicion, how to maintain the stack, and even when it is worth destroying the stack. One stand-out routine is the Christ-Aronson Aces, which doesn't require the memorization of the stack, but keeps the stack intact, even though it gives the illusion of the deck being well-mixed throughout the routine.

The video concludes with closing remarks, including a reminder of the various memorized deck principles employed, and a full chart of the Aronson Stack order.

This DVD is a very valuable resource on the memorized deck. Whether you currently do memorized deck work, or are seriously considering it, I suggest getting Sessions With Simon, Vol. 3 as an introductory purchase, followed closely by Mnemonica for further research.

It feels like a lazy weekend, so today, we'll just relax with some pleasant mental diversions.

Let's start off with 50 States in 10 Minutes, in which you have to list as many U.S. states as you can in 10 minutes.

Less challenging, yet equally puzzling, is Fido's Mind Reading (Flash required). Like these mind reading feats? You may also like Andy Naughton's Flash Mind Reader (Flash required).

Is your brain still hungering for more? Check out Google's Puzzle Gadgets for a nearly endless supply of mentally challenging puzzles!

It's Pi Day, which means it's the 2nd blogiversary of Grey Matters! Grey Matters has come a long way in those two years, and it's still growing.

To kick off the celebration, there are many changes over at Grey Matters Online Store. Do you want to learn and remember 400 Digits of Pi? Then you'll appreciate the new and permanent $10 drop in price for my memory course, Train Your Brain and Entertain! Yes, it is now only $29.95, which also applies to the downloadable version at Lybrary.com, too.

Maybe you've remembered the digits, and just need a way to show off your knowledge. In that case, you can wear Pi. The prices on all the T-shirts on the site have been reduced, so if you've been hesitating purchasing a shirt, check out the new lower prices!

Speaking of the Pi designs, I've added a shirt with the Pi Chart on the front, in both women's and men's clothes, in response to numerous requests.

For that matter, what is Pi good for? Well, it's central to the new Pizza Theorem section, for one. I first mentioned the Pizza Theorem earlier this month.

Need some help celebrating Pi Day? Start with PiDay.org, and then move on to TeachPi.org and Pi Nation! If it helps you learn, you can even sing about Pi (Flash required). Naturally, there's plenty of Pi to go around both on the Grey Matters Blog and Grey Matters Videos.

Before I go, let's not forget that it is the 128th anniversary of Einstein's birth today.

Have a happy and fun Pi Day!

Could free flashcard memorization be the killer app of early 2007? If you look at all the recent entries I've posted on flashcard programs, you might be tempted to think just that. About 1/3 of my post since late January have focused on free flashcard programs.

I've found cueFlash to be well thought-out. While not as feature-rich as some of the flashcard programs I've reviewed, it handles the basics quite well. The cueFlash demo video (Flash required) explains it quite clearly.

There's also The Amazing Flash Card Machine (TAFCM). What makes TAFCM stand out is its ability to upload text files anc convert them into text files. This would work well with applications which have the ability to output .txt files, such as Ebbinghaus, or your favorite database.

I'll keep you up to date on online memory tools as I learn about them. If you know of ones I haven't covered yet, please e-mail me or leave me a message in the comments box!

The 3rd Carnival of Mathematics is now up!

Michi has made this carnival 2.5 times better than the previous Carnivals by breaking the posts up into five halves!

I've discovered yet another site to add to my list of free online memory tools. The site is called ProProfs, whose focus is free high quality education. While they offer a wide variety of educational tools on their site, readers of this site will find their QuizSchool and Flashcards sections especially interesting.

With the Flashcards section, you create simple two-sided flashcards, which you can then quiz yourself and share with others. When the Quiz starts, you can decide whether to have the cards shuffled, or presented in their original order. During the quiz, you can switch which side is displayed first, as well as mark cards for review later. To get a better idea of the self-explanatory interface, try quizzing yourself on the U.S. states and capitals.

QuizSchool is more advanced, but is still easy to use. As you'll see in my simple Pi Digit Quiz, you can have both fill-in-the-blank and multiple choice questions, and your score is kept automatically.

While you have to register to create your own flashcards and quizzes, registration is free. It's easy to let anyone take the tests, as no registration is required. All you have to do is provide a link. The process of creating the quizzes and flashcards is easy and straightforward, with plenty of assistance right in the interface itself.

It's even possible to add your quizzes and flashcards to your own website. You will need to be familiar with the use of the IFRAME tag to add the quiz to your web page. Used properly, you'll get a result like this:



Unfortunately, there is no simple embed code box, like the ones you find on video sites. However, you can make it easier for people to add your quiz or flashcard to their site by providing the code, as I've done on the last page of the Pi Digit Quiz.

If you've been looking for adding a little more interactivity to your site, I definitely recommend checking out ProProfs' Flashcards and QuizSchool sections!

Robert H. Nutt's 1943 book, How to Remember Names and Faces: How to Develop a Good Memory, is now available online for free!

Despite the name, this book is not only about remembering names and faces. It's actually about developing a better memory overall. It's divided into two main sections, The Mental Filing System, containing 20 chapters, and How To Remember Names And Faces, containing 13 chapters.

Instead of teaching the standard Peg System, his approach for numbers involves objects, most of which are easily associated with their numbers. 13, for example, is easily associated with floor, since most of us have heard that many hotels won't have a 13th floor. Also, these pegs are taught over many chapters, so that you learn them and use them more effectively.

The section on remembering names and faces is one of the most thorough I've seen. If you've read works on remembering names and faces before, much of the advice will seem familiar, but there are a wider variety of techniques here.

One of the best things about this book, beyond just the memory training itself, is the frequent use of rich anecdotes. These really drive home the power of a trained memory, as well as the disadvantages of an untrained memory.

According to the home page, this ebook will only be free for a limited time, so you may wish to download and save it. It should be available longer than the previous free memory ebook, however.

Sure, Mathworld is a great resource for learning about things like Pi, but that doesn't mean it's all dry and boring. As a matter of fact, if you look closely, Mathworld is a surprisingly amusing site.

It was the Athanasuis Kircher Society that first alerted me to Tupper's Self-Referential Formula. This unusual formula, when plotted on a graphing calculator will form an image of the formula itself!

Next, Mikhail Klassen alerted me to three different amusing numerical laws:

Strong Law of Small Numbers: The first strong law of small numbers (Gardner 1980, Guy 1988ab, Guy 1990) states "There aren't enough small numbers to meet the many demands made of them."

The second strong law of small numbers (Guy 1990) states that "When two numbers look equal, it ain't necessarily so."

Law of Truly Large Numbers: With a large enough sample, any outrageous thing is likely to happen (Diaconis and Mosteller 1989).

Frivolous Theorem of Arithmetic: Almost all natural numbers are very, very, very large.

Naturally, these examples led me to explore the site further. First, I ran across the Pizza Theorem (the second one), which states:

the [formula for the] volume of a pizza of thickness a and radius z [is]:
pi z z a

The Pizza Theorem is also listed on the Self Recursion, along with the several questions that employ self-recursion to give their respective answers:

1. In 1978, Raymond Smullyan wrote a book about logical puzzles. What is the name of this book?

2. I am the square root of -1. Who am i?

3. What would the value of 190 in hexadecimal be?

4. Twenty-nine is a prime example of what kind of number?

5. The reciprocal of the square root of two is half of what number?

6. How many consonants are in “one”? How many in “two”? And how many in “three”?

7. What do you do to the length of an edge of a cube to find its volume?

Amusingly, if you look in the See Also section of the self-recursion page, it links to itself.

I don't want to ruin too much of your enjoyment and exploration, so I'll leave you for now with the Mathematical Humor index.