6700417

This number is a prime.

6700417 is a prime co-factor (with 641) of 2^(2^5)+1 or the Fermat number F₅. This was the first Fermat number shown to be composite, which was discovered by Leonhard Euler in 1732, less than 100 years after Pierre Fermat claimed that he believed all numbers of the type [2^(2^n)+1] were prime. [Dobb]