# 131333131

This number is a prime.

The smallest "plus sign prime."

1A31333131

*plus sign prime*is a palindromic prime of n^2 digits (n, odd > 2) arranged left-right, top-down, in an n-by-n array, where the central row and column make a plus sign (+) and consist of identical digits b. The other digits of the array are identical digits different from b. Thus, an order 3 plus sign prime is of the form ababbbaba, order 5 of the form aabaaaabaabbbbbaabaaaabaa, etc. [Loungrides]

(There is one curio for this number that has not yet been approved by an editor.)

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell