Numbers are wonderfully malleable things. My favorite mental game is 24, because it’s so easy to play with Chicago’s four-digit addresses and Illinois’ four-digit license plates. Simply take any four-digit number you see (ignore the ones with zeros but not the ones with repeated digits), and using only the basic symbols of addition, subtraction, multiplication, and division, create an equation in which the digits equal 24. You usually can. For instance, the digits 1, 2, 3, and 4 can be made to equal 24 simply by doing this: 1 x 2 x 3 x 4. But as I said, numbers being malleable — or perhaps treacherous is a better word — they can also be manipulated to equal every number from zero up to 24 — and some numbers beyond it.