33837...42891 (56-digits)

This number is a prime.

               338374 6409486665 5412810571 6448226708 1046924847 8083542891

Just showing those entries submitted by 'Andersen': (Click here to show all)

This prime starts the largest known Cunningham chain of length 12 as of 2008: (8428860*127# + 212148902055090) * 2^n + 1, for n = 0 to 11. It also contains the largest known chain of length 11 which was actually the goal. There just happened to be a 12th prime. The chains are of the second kind. [Andersen]