Thought I would list all the guesses so far. There are a few double up's but the OP never said a unique number so that's ok.
My guess is 73
Numbers guessed so far:
42, 45, 47, 48, 49, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 87, 88, 89, 92, 93, 94, 95, 96, 97, 98, 99, 101, 102, 107, 113, 123, 129, 178