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Mersenneplustwo factorizations

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Last update: 2019-03-05

The Mersenneplustwo factorizations is a distributed computing project, which tries to factor numbers of the form: 2p+1 (with p being a prime, as well as simultaneously 2p-1 being prime). All such numbers are divisible by 3 since 2p-1 is not divisible by 3 (it's assumed to be prime) and 2p is not divisible by 3 (it's only prime factor is 2).

It is managed by James Wanless (Bearnol).

How to participate

Participants use ECMclient to automatically download numbers, do ECM curves on them and upload them again.


As of this moment (2005-09-12), about 8GHz is being dedicated to this project. Update needed or remove! More recently (2019-03-05), about 100GHz on the ECMNet.


Best results so far include 37-digit factor of M9941+2 (FDBid) found by ECMNet, as well as 36-digit factor of M11213+2 (FDBid) found using mprime (the linux version of Prime95 by George Woltman).

More recently, a 41-digit factor of M110503+2 (FDBid) was also found by ECMNet.

External links