16660...69091 (35-digits)

This number is a prime.

                                      16660 6116660811 6680011668 8691669091

{16660611666081166800116688691669091, 16690911668869166800116660811666061} is the smallest case of a pair of 35-digit primes concatenating in ascending and descending order five 7-digit invertible primes, i.e., {1666061, 1666081, 1668001, 1668869, 1669091}. [Bajpai]