| The Erdös Number Project | Great Internet Mersenne Prime Search |
| Reminiscences of Paul Erdös | Largest Known Prime |
| Srinivasa Ramanujan | Largest Sophie Germain Prime |
| Perfect Numbers[2] [ ] [ ] | Prime Factoring |
| Pi Computing Pi | Ulam's Problem |
| Unit Fractions[2] [ ] | Integrals.Com |
| Math Forum Internet Collection - varied (broken link) | |
| Smith Numbers | Fermat Little Theorem |
| Twin Primes | Fermat's Last Theorem |
| Harmonic Series | Asymptotic Formulae |
| Geometric Series | Fibonacci Numbers |
| Friendly Numbers | Ruth-Aaron Pairs |
| Bin-packing Problem | Ramsey Theory |
| Beale Cyphers | Royal Holloway College, Info Security Group (broken link) |
| Bletchley Park | National Cryptologic Museum (NSA) |
| Alan Turing | America Cryptogram Association (ACA) |
| Eingma Emulators [1] [2 (broken link)] | Cryptologia (broken link) |
| Phil Zimmermann & PGP (broken link) | Cryptography FAQ |
| Electronic Frontier Foundation (EFF) | RSA Laboratory's FAQ |
| Centre for Quantum Computation | Yahoo Security & Encryption |
| Other Crypto Links |