51091297865364919801

This number is a prime.

                                                       5109129786 5364919801

51091297865364919801 = (0+1)! + (2+3)! + (4+5)! + (6+7)! + (8+9)! + (10+11)! is the prime sum of the first 11 digits in ascending order, in paired-sum factorials. [Post]