Largest known probable prime Mersenne Cofactors  (proper divisor of 2p-1 with p prime)

 Cofactor

 Digits

 When

 Found by

 (21168183-1)/54763676838381762583

 351639  

 01/2011  

 Matthias Wurtinger

 (2684127-1)/23765203727

 205933  

 04/2009  

 Jens Kruse Andersen

 (2406583-1)/813167

 122388  

 02/2009  

 Jens Kruse Andersen

 (2271549-1)/238749682487

 81734  

 02/2009  

 Jens Kruse Andersen

 (2271211-1)/613961495159

 81631  

 02/2009  

 Jens Kruse Andersen

 (2221509-1)/292391881

 66673  

 02/2009  

 Jens Kruse Andersen

 (2173867-1)/52536637502689

 52326  

 06/2005  

 Donovan Johnson

 (2136883-1)/536581361

 41198

 05/2005

 Donovan Johnson

 (2130439-1)/260879

 39261

 05/2005

 Donovan Johnson

 (2106391-1)/286105171290931103

 32010

 05/2005

 Donovan Johnson

 (287691-1)/806957040167570408395443233

 26371

 11/2009

 D. Broadhurst and W. Edgington

 (286371-1)/41681512921035887

 25984

 05/2005

 Donovan Johnson

 (286137-1)/20021531730209833250959969231661791

 25896

 02/2011

 D. Broadhurst and W. Edgington

 (282939-1)/883323903012540278033571819073

 24938

 11/2009

 D. Broadhurst and W. Edgington

 (287005-1)/(217401-1)/31

 20952

 07/2007

 Lelio R. Paula

 (270129-1)/(23691-1)/524287

 19995

 12/2007

 Lelio R. Paula

 (263703-1)/42808417

 19169

 05/2005

 Donovan Johnson

 (258199-1)/237604901713907577052391    

 17497

 05/2005

 Donovan Johnson

 (285881-1)/(228627-1)/7

 17235

 12/2007

 Lelio R. Paula

 (257131-1)/61481396117165983261035042726614288722959856631

 17152

 09/2009

 D. Broadhurst and W. Edgington

 (270617-1)/(223539-1)/7

 14172

 12/2007

 Lelio R. Paula

 (269933-1)/(223311-1)/7

 14034

 12/2007

 Lelio R. Paula

 (241521-1)/41602235382028197528613357724450752065089

 12459

 09/2010

 D. Broadhurst and W. Edgington

 (241263-1)/1379707143199991617049286121

 12395

 05/2004

 Donovan Johnson

 (242991-1)/(23307-1)/8191

 11943

 12/2007

 Lelio R. Paula


All probable prime cofactors on this page are listed on Henri Lifchitz's Top 10000 PRPs page. Click here to view.


20 largest known prime Mersenne cofactors (The Prime Pages)
Will Edgington's Mersenne Page
Biography of Marin Mersenne
Main page


Last updated on August 12, 2011
Donovan Johnson