18986...91611 (42-digits)

This number is a prime.

                              18 9868118818 8118808811 6906911681 8911191611

The smallest invertible prime that is the reverse concatenation of six consecutive strobogrammatic primes: (1898681, 1881881, 1880881, 1690691, 1681891, 1191611). [Bajpai]