Mersenne: Factoring

[Jim Howell]

[Wed 14 Jun 2000, Paul Leyland writes] Today I found this number 3756482676803749223044867243823 with ECM and B1=10,000.  It has two factors, each of 16 digits, which could *not* have been found by trial division in any reasonable time.   -------------   I use a program called "factor.exe", which uses several factoring methods.  It factors the above number within several seconds.  (For this number, the factors are found with the P-1 method.)  In case anyone is interested, the factors are  1483398061194277 and 2532349728015299. This program runs on Windows, and can be downloaded from Chris Caldwell's main page, at:   http://www.utm.edu/research/primes   Go down to section 4, (Software), and look for "factor.exe", described as a DOS program, but it actually runs in a Command Window on Windows 95 and later, and (probably) not under actual DOS.  I find "factor.exe" quite useful for factoring small numbers (it will accept numbers up to about 130 digits). --Jim