The Penguin Dictionary of Curious and Interesting Numbers (Penguin Press Science)

Everything you wanted to know about numbers is included in this book, including aliquot sequences, the cattle problem, Pascal's triangle, and the Syracuse algorithm.

Why was the number of Hardy's taxi significant? Why does Graham's number need its own notation? How many grains of sand would fill the universe? What is the connection between the Golden Ratio and sunflowers? Why is 999 more than a distress call?

All these questions and a host more are answered in this fascinating book, now revised with nearly 200 extra entries as well as 250 additions to the original entries. There is even a comprehensive index for those annoying occasions when you remember the name but can't recall the number.