140737488356207

This number is a prime.

                                                            14073 7488356207

According to the textbook "Elements of Number Theory" by Pettofrezzo and Byrkit, the largest known twin prime pair in 1975 was {140737488353699, 140737488353701}. The lesser element in the succeeding twin prime pair after a computer algebra system (CAS) calculator search encompassing in excess of five dozen primes is 140737488356207. Of course, such a fifteen-digit integer was quite a challenge for the technology available then. [Schiffman]