41

This number is a prime.

The sixth prime digit sum of the contiguously concatenated digits of the Copeland-Erdős Constant, (i.e., 0.2357111317192...) has SOD(235711131719) = 41, and is the smallest such sum to have an adjacent sum of digits similarly formed, i.e., SOD(2357111317192) = 43, which is only a single-digit longer. Note that {41, 43} are twin primes. [Harrison]