Fermat numbers are F

_{n} = 2

^{2n} + 1, n = 0, 1, 2, â€¦ . Fermat incorrectly stated that they were all prime, but Euler showed that F

_{5} was divisible by 641. From there up to F

_{32} they are all composite and it is very likely that only finitely many are prime. Gauss showed that the number of sides of a regular polygon that could be constructed with straightedge and compass alone had to be a power of 2 times a product of distinct Fermat primes. Fermat numbers have many properties and even have applications.

This admirable book contains what must be everything that is worth knowing about Fermat numbers. (There are eighteen pages of references.) Though the authors claim it is for a general mathematical audience, readers should be familiar with elementary number theory. It contains a wealth of fascinating results, e.g., that 78557×2^{n} + 1 is composite for all n, and that the rows of Pascalâ€™s triangle modulo 2 give, when read as integers in base 2, the sequence of the number of sides of constructible regular polygons. The Foreword, by Alena Å olcovÃ¡, is an excellent account of Fermatâ€™s life and works.

The authors, and the series editors, Jonathan and Peter Borwein, deserve credit and praise for producing what will be the definitive work on the subject for many years to come.

After retiring from DePauw University, Woody Dudley is living in Florida and continues to be active in the MAA and in teaching calculus.