61000...00019 (79-digits)

This number is a prime.

                                                                   610000000
0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000019

The largest strobogrammatic prime less than a googol formed by inserting n zeros between 61, 19, that are the terms of the only pair of double-digit prime rotative twins, (case n=75). [Loungrides]