137438691329

This number is a prime.

                                                               13 7438691329

+ The largest known prime number (emirp) of the form (2^(p-1))*(2^p-1)+1, where 2^p-1 is a Mersenne prime. Such numbers are called right perfect primes; the others are 7, 29, and 33550337. [Loungrides]

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