Burt Kaliski Jr. (@modulomathy) 4/20/12 5:23 PM #math trivia for #April20: #111 is a prime in every base less than 10, except for which two? The base-10 values corresponding to 111 in bases 1 to 9 are 3,7,13,21,31,43,57,73,91 There are actually three non-primes in this list, the ones corresponding to bases 4, 7, and 9. … Continue reading