Analyze Math, Cram, Math Is Fun and the National Council of Teachers of Mathematics are websites to learn factors for numbers one through 100, as of 2015. Textbooks and workbooks also have information on factorization.
Analyze Math has examples for factorization and a calculator to display prime factors. Cram uses online flashcards, tests and games to aid in memorization of factors. Math Is Fun has tables of factors and multiples for memorization and explanations of factorization. The National Council of Teachers of Mathematics has interactive games to learn factorization. Players can choose to play against another person or the computer.