One is the number of times snails have sex in their lives. Thirty is the number of pieces of legos that each person in the world would get if we split up the current supply evenly. Eighty-three is the percentage of people hit by lightning who are men. Adam Spencer's *Book of Numbers* provides entertaining facts about the numbers 1 through 100. For those of you that are more serious this book is also filled with mathematical facts and definitions as they relate to the numbers 1 through 100. For example, seven is a Mersenne prime. Forty-seven is an Ulam number. Seventy is a weird number (an abundant number that isn't equal to the sum of any of its divisors).

This book is arranged into 100 chapters each one or two pages long, beginning with a number from 1 to 100 prominently displayed at the top of the page. That chapter is then devoted to trivia, humor, and mathematical facts about the number. There are similarities between this book and *The Penguin Dictionary of Curious and Interesting Numbers* by David Wells, and, in fact, Spencer references Wells. But even if you own *The Penguin Dictionary*, it still worth getting the *Book of Numbers*. The layout and design of the *Book of Numbers* makes it much more enticing to pick up and read about a number. Wells' book certainly has more mathematics, and while more mathematics would be nice, there is plenty of math in Spencer's book. *The Penguin Dictionary* goes well beyond the 100 numbers that the *Book of Numbers* limits itself to. Yet, there are 19 numbers in the *Book of Numbers* that are skipped in *The Penguin Dictionary*. Ultimately, however, the big difference is the trivia and humor in Spencer's book, which is what makes the book fun. If you are trying to engage those that are a little math shy, it is like eating your broccoli with cheese sauce. By the way, thirty-six is the age of Homer Simpson.

I found this book to be an excellent classroom supplement. At the beginning of the first class I read the facts about the number one. Of course, the students enjoyed the snail fact. Each day after that the students chose one number to be read before class, and they were responsible for keeping track of the numbers that had already been selected. They never let me forget to read a number and students would even run back to my office, only a hallway away, to get the book if I forgot it. This was a great way to start out class as we all learned some extra mathematics. For instance, we learned about the 3x + 1 problem, that 16 is the only number that can be written in a reverse power, and about lucky numbers. At the same time we acquired some interesting scientific and historical facts, and often had a good laugh.

I recommend putting this book anywhere students tend to hang around (outside offices or in a math study room). You can get something out of this book in under a minute and I think you will find that the book becomes a topic of conversation among your students. They might even start asking you about the math in the book. This book would be a great choice if your department gives a book, or other gift, to graduating seniors or math award winners. Thirteen is about how many dollars this book costs and it is worth it.

By the way, if you have been worrying about those poor old snails: Twelve is the number of hours it lasts.

By the way, if you have been worrying about those poor old snails: Twelve is the number of hours it lasts.

Thomas J. Pfaff is Assistant Professor of Mathematics at Ithaca College. He can be reached at tpfaff@ithaca.edu.