11111...11111 (25-digits)

This number is a prime.

                                                 11111 1111100600 1111111111

The smallest almost minus sign prime of order 5. (An almost minus sign prime is a palindromic prime of n^2 digits arranged left-right, top-down, in an n-by-n array, whose all the digits except for the middle row digits, are identical, equal to a, and the digits of the middle row (except for the central digit are identical too, equal to b. [Loungrides]