103

This number is a prime.

The smallest prime which cannot be expressed as a sum or difference of two numbers which contain only the factors 2 and 3. That is, 103 cannot be written in either of these forms: 2^x + 3^y = 103, 2^x - 3^y = 103, 3^y - 2^x = 103, 2^x3^y +/- 1 = 103. [Diloreto]