46931...13377 (23-digits)

This number is a prime.

                                                   469 3163567786 4055013377

+ The first known factor of F31 was discovered on April 12, 2001, by A. Kruppa using a sieving program developed by T. Forbes. (The Fermat numbers grow so fast that our only hope of showing them not prime is by finding a factor.)

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