Integer Factorization Records - Numbers of A Special Form

Numbers of A Special Form

12151 − 1, of 542 bits (163 digits), was factored between April and July 1993 by a team at CWI and Oregon State University.

2773 + 1, of 774 bits (233 digits), was factored between April and November 2000 by 'The Cabal', with the matrix step done over 250 hours on the Cray also used for RSA-155.

2809 − 1, of 809 bits (244 digits), had its factorisation announced at the start of January 2003. Sieving was done at the CWI, at the Scientific Computing Institute and the Pure Mathematics Department at Bonn University, and using private resources of J. Franke, T. Kleinjung and the family of F. Bahr. The linear algebra step was done by P. Montgomery at SARA in Amsterdam.

6353 − 1, of 911 bits (275 digits), was factored by Aoki, Kida, Shimoyama and Ueda between September 2005 and January 2006 using SNFS.

21039 − 1, of 1039 bits (313 digits) (though a factor of 23 bits was already known) was factored between September 2006 and May 2007 by a group including K. Aoki, J. Franke, T. Kleinjung, A. K. Lenstra and D. A. Osvik, using computers at NTT, EPFL and the University of Bonn.

21061 − 1, of 1061 bits (320 digits) was factored between early 2011 and 4 August 2012 by a group headed by Greg Childers at CSU Fullerton, using the nfs@home BOINC project for about 300 CPU-years of sieving; the linear algebra was run at the Trestles cluster at SDSC and the Lonestar cluster at TACC.