12345...23451 (42-digits)

This number is a prime.

                              12 3456790123 4567901234 5679012345 6790123451

Just showing those entries submitted by 'Rivera': (Click here to show all)

R(2)+R(3)+R(4)+ ... +R(42) is a 42-digit prime, where R(n) is a repunit number. [Rivera]