How many people do you need in a room before there'll be a birthday in common? Why is 70 weird, and what can we do about it? How can 56 people eat 1 pizza? In 100 bite-size chapters of no more than three pages each, Adam Spencer gives each number, 1 to 100, its place in the limelight. For example, take 65. It's the constant of a 5 x 5 "magic square" -- a square that contains the numbers 1 to 25, where all the rows and columns and each diagonal add...