11111...11111 (169-digits)

This number is a prime.

                                             111111111 1111111111 1111111118
8888888811 1183333333 8111183888 8838111183 8111838111 1838111838 1111838111
8381111838 8888381111 8333333381 1118888888 8811111111 1111111111 1111111111

      1 1 1 1 1 1 1 1 1 1 1 1 1
      1 1 1 1 1 1 1 1 1 1 1 1 1
      1 1 8 8 8 8 8 8 8 8 8 1 1
      1 1 8 3 3 3 3 3 3 3 8 1 1
      1 1 8 3 8 8 8 8 8 3 8 1 1
      1 1 8 3 8 1 1 1 8 3 8 1 1
      1 1 8 3 8 1 1 1 8 3 8 1 1
      1 1 8 3 8 1 1 1 8 3 8 1 1
      1 1 8 3 8 8 8 8 8 3 8 1 1
      1 1 8 3 3 3 3 3 3 3 8 1 1
      1 1 8 8 8 8 8 8 8 8 8 1 1
      1 1 1 1 1 1 1 1 1 1 1 1 1
      1 1 1 1 1 1 1 1 1 1 1 1 1

A triadic square-congruent prime of order 13. [Patterson]