99999199999

This number is a prime.

                                                                9 9999199999

The largest palindromic prime less than a googol that has palindromic prime length. [Patterson]

Prime numbers of the form N_d (n, m) = 10^(2*n + m) - d *10^n - 1, e.g., 99999199999, are of interest to the recreational mathematics community.