27 Mar
2010
27 Mar
'10
4:30 p.m.
A 54-digit prime factor of F12 has just been found with GIMPS' ECM. It's the sixth known prime factor of F12. The 1133-digit cofactor is composite. So F12 is still the smallest Fermat number that we cannot factor completely. See http://mersenneforum.org/showthread.php?t=13215 The discovery happened only a day after a factor of F22 was found (also with GIMPS' ECM) and 24 years after Robert Baillie found the fifth known factor by Pollard's p-1 method. Warut