True: 1 3 511 5 7 9 15 51 33 False: 2 4 2017 91 6 8 551 552 11 512 19 123456789 12 113311 151
MD5::Digest(input).chars.last.ord % 2 == 0
def c(n):i=bin(n)[2:];return i==i[::-1]
def c n;i=n.to_s(2);n==n.reverse;end