Other
Eratosthenes' Prime Number Sieve
Discover all the primes up to the number 400 by using this interactive table. Simply click on a number and its multiples disappear.
SMART Technologies
Smart: Factors and Multiples
Students are introduced to prime numbers, composite numbers, prime factorization, greatest common factor, and least common multiple in this SMART whiteboard activity.
Shodor Education Foundation
Shodor Interactivate: Factorize
This Shodor site gives a brief explanation of factorization, and it allows you "to find all of the factorizations of a given number and then draw the product as the area of a rectangle on a grid."
National Institute of Educational Technologies and Teacher Training (Spain)
Ministerio De Educacion: Divisores Y Primos
Reinforce your knowledge on prime numbers and their divisors.
Elias Saab
Math Drills: Prime Factorization Quiz
This site is an interactive quiz which provides students with a prime factorization problem. Students input their solution and have the program evaluate it. Hints are available if the student needs them, and explanations are provided...
Curated OER
Clip Art by Phillip Martin: Prime and Composite Numbers
A clipart illustration by Phillip Martin titled "Prime and Composite Numbers."
Wyzant
Wyzant: Prime Factors Calculator
Students input a number to be factored and the WyzAnt calculator does the rest. Limitations include the fact that numbers which are negative or which contain primes bigger than 541 cannot be handled.
ClassFlow
Class Flow: Number Sense Related to Division
[Free Registration/Login Required] This flipchart introduces divisibility, primes and composites, averages, and estimating quotients.
National Institute of Educational Technologies and Teacher Training (Spain)
Ministerio De Educacion: La Criba De Eratostenes
Reinforce your knowledge about prime and composite numbers. Geogebra plugin required.
Wolfram Research
Wolfram Math World: Euclid's Theorems
This site from MathWorld.com provides a description of the theorems of Euclid and his theories of prime and composite numbers.
Alabama Learning Exchange
Alex: My Favorite Number
The activity allows students to review many of the number theory concepts. Students will pick a composite number write verbal expressions about the number, find the factors, prime factorization, list multiples, draw a cartoon character...
Math Open Reference
Math Open Reference: Number
Resource defines numbers into two main categories, counting numbers and scalars. It also gives examples of number notation.
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Fractions, Number Theory
Twenty problems presented on the topics: factors, prime/composite and many aspects of working with fractions. They are given with each step to the solution cleverly revealed one at a time. You can work each step of the problem then click...
PBS
Pbs: Greatest Common Factor
In this video, learn how to find the greatest common factor of two numbers. Then, see how this can be used to solve problems with large numbers. In the accompanying classroom activity, students learn to find prime factors using factor...