4327

This number is a prime.

Largest known prime partial sum of number of self-avoiding walks on square lattice, summing all such walks from the definitional minimum 4 through 19 steps: 0 + 0 + 0 + 1 + 0 + 0 + 2 + 7 + 12 + 14 + 36 + 95 + 226 + 501 + 1056 + 2377 = 4327 is prime. [Post]