#math trivia for #February16: 47 is the third prime this “decade” (the 40s). Why are the 10s, 40s and 70s so popular for primes? — Burt Kaliski Jr. (@modulomathy) February 16, 2012 The 10s, 40s and 70s each have at least three primes: 10s:  11, 13, 17,  19 40s:  41, 43, 47 70s:  71, 73, … Continue reading →