25931

This number is a prime.

The smallest prime partial sum of number of collections containing two or more nonempty subsets of {1,2,...n} that are pairwise disjoint: 1 + 7 + 36 + 171 + 813 + 4012 + 20891 + 115463 + 677546 + 4211549 = 5030489 is prime. [Post]