11111...11111 (289-digits)

This number is a prime.

                                                                   111111111
1111111112 2222222222 2222112333 3333333333 2112344444 4444443211 2348888888
8843211234 8999999984 3211234895 5555984321 1234895666 5984321123 4895676598
4321123489 5666598432 1123489555 5598432112 3489999999 8432112348 8888888843
2112344444 4444443211 2333333333 3333211222 2222222222 2211111111 1111111111

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

     1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
     1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1
     1 2 3 3 3 3 3 3 3 3 3 3 3 3 3 2 1
     1 2 3 4 4 4 4 4 4 4 4 4 4 4 3 2 1
     1 2 3 4 8 8 8 8 8 8 8 8 8 4 3 2 1
     1 2 3 4 8 9 9 9 9 9 9 9 8 4 3 2 1
     1 2 3 4 8 9 5 5 5 5 5 9 8 4 3 2 1 
     1 2 3 4 8 9 5 6 6 6 5 9 8 4 3 2 1 
     1 2 3 4 8 9 5 6 7 6 5 9 8 4 3 2 1
     1 2 3 4 8 9 5 6 6 6 5 9 8 4 3 2 1
     1 2 3 4 8 9 5 5 5 5 5 9 8 4 3 2 1
     1 2 3 4 8 9 9 9 9 9 9 9 8 4 3 2 1
     1 2 3 4 8 8 8 8 8 8 8 8 8 4 3 2 1
     1 2 3 4 4 4 4 4 4 4 4 4 4 4 3 2 1
     1 2 3 3 3 3 3 3 3 3 3 3 3 3 3 2 1
     1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1
     1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 

The smallest square-congruent prime containing all non-zero digits. [Hartley]