Prime Number

http://www.softschools.com/math/prime_numbers/prime_numbers_up_to_100/

Multiples

http://www.sheppardsoftware.com/mathgames/multiple/multiple_frenzy.htm

Lowest Common Multiple (LCM)

Let's play the Snow!!~~

http://www.fun4thebrain.com/beyondfacts/lcmsnowball.html

Factors

http://www.math-play.com/Factors-Millionaire/Factors-Millionaire.html