Digital Divisibility Tests
- From Carlos Rivera's Prime Puzzles and Problems collection. Carlos asks for the general divisibility rules for any prime number.
- http://www.primepuzzles.net/puzzles/puzz_101.htm

Divisibility Tests
- From the Furman University Electronic Journal of Undergraduate Mathematics. Apoorva Khare's paper is available as an abstract, DVI, and PostScript.
- http://math.furman.edu/~mwoodard/fuejum/textv/volume3text.html

Explaining the Divisibility Rules
- Proof of the elementary division rules, plus some lesser-known rules for larger divisors and other bases.
- http://mathforum.org/k12/mathtips/ward.html

Divisibility War
- A card game to teach divisibility rules.
- http://edweb.sdsu.edu/courses/edtec670/Cardboard/card/d/Divisibility.html

Divisibility Criteria
- Ways of telling whether one number divides another without actually carrying the division through, constructed here in terms of the digits of the number.
- http://www.cut-the-knot.com/blue/divisibility.html