Way more fun than it should be. Multiples of 3 are the worst, at least for me. Using the trick to check those helps a lot (sum the digits, it's div-by-3 iff the

Way more fun than it should be. Multiples of 3 are the worst, at least for me. Using the trick to check those helps a lot (sum the digits, it's div-by-3 iff the sum of digits is div-by-3).