Known Amicable Pairs
- A listing of all the known pairs of numbers, each of which is the sum of the aliquot divisors of the other. Complete for smaller numbers, and extending beyond 200 digits.
- http://amicable.homepage.dk/knwnc2.htm

Discovery of a Lost Factoring Machine
- Built by a French amateur, E.-O. Carissan, around 1919. Shallit, Williams and Morain include photographs and references to their paper.
- http://www.cs.uwaterloo.ca/~shallit/Papers/carissan.html

RSA Laboratories Factoring Challenge
- Numbers representative of those used in the RSA cryptosystem are offered for factor attempts with prizes. A Partition List challenge is also provided in order to encourage work on factoring in general.
- http://www.rsasecurity.com/rsalabs/node.asp?id=2092

Factoring Fermat Numbers
- Cash prizes for new factors of Fermat numbers Fn, for n = 12 through 22.
- http://www.perfsci.com/freegoods.htm#fermat

Integer Factorization
- Paul Leyland's list of his own and other factorisations.
- http://www.leyland.vispa.com/numth/factorization/main.htm

Factorization of F10
- F10 = 2^(2^10) + 1 is the 10-th Fermat number. Richard Brent describes his discovery of the two largest factors.
- http://web.comlab.ox.ac.uk/oucl/work/richard.brent/F10.html

Computing Aurifeuillian factors
- Algorithm that finds non-trivial factors of certain numbers of the form a^b +/- 1.
- http://web.comlab.ox.ac.uk/oucl/work/richard.brent/pub/pub127.html

Factorizations of Near-repdigit Numbers
- Factorizations of numbers composed of all the same digit except first and/or last.
- http://homepage2.nifty.com/m_kamada/math/factorizations.htm

Factoring Papers
- Links to papers on the theory and practice of factoring.
- http://www.crypto-world.com/FactorPapers.html

The XYYXF Project
- A collaborative project to produce the factorizations of x^y + y^x for 1<y<x<101.
- http://xyyxf.at.tut.by/

Factorization of RSA-155
- Announcement of factorization of a 512-bit RSA key using the General Number Field Sieve (GNFS).
- http://www.crypto-world.com/announcements/RSA155.txt

FactorWorld
- Dedicated to algorithms and computational results on integer factorization. Includes links to papers, downloadable software, and online resources.
- http://www.crypto-world.com/FactorWorld.html

Fermat Search
- Leonid Durman's Fermat number factoring site and program.
- http://www.fermatsearch.org/

Factorization Using the Elliptic Curve Method
- Java applet that can be used to find 20- or 30-digit factors of numbers or numerical expressions up to 1000 digits long. It also computes the number and sum of divisors, the Euler's totient and moebius functions, and the decomposition of the number in a s
- http://www.alpertron.com.ar/ECM.HTM

I Love Binary, Primes, and Factors
- Divisibility, primes and binary numbers.
- http://home.earthlink.net/~usondermann/binary.html

N!+-1 Factoring Status
- Factoring efforts that have been made so far on numbers of the form n!+-1 using ECM factoring.
- http://www.uow.edu.au/~ajw01/ecm/curves.html

Sierpinski Problem
- Sierpinski proved there exist infinitely many odd integers k such that k*2^n+1 is composite for every n. Ray Ballinger coordinates a search to prove or disprove whether k=78557 is the smallest solution.
- http://www.prothsearch.net/sierp.html

Factoris
- Online calculator that factorizes large numbers, specified by formula.
- http://wims.unice.fr/~wims/wims.cgi?lang=en&module=tool/algebra/factor.en&cmd=new&