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."
Discovery Education
Discovery Education: Web Math: Factor an Integer
WebMath gives a calculator to give all the factors of a number. Drop down menu can select just prime factors of number entered. Also discusses the definition of a factor.
Wolfram Research
Wolfram Mathworld: Prime Factorization
This site gives a wonderful explanation of prime factorization including a very helpful table in understanding prime decomposition. Look further down the page to get information on Gaussian primes.
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.
Amby Duncan-Carr
Prime Factorization: Amby's Resources
What is prime factorization? This site goes through a step-by step process explaining different ways to find the prime factorization.
Homeschool Math
Homeschool Math: Prime Factorization
This site contains a free lesson on Prime Factorization in which students learn by doing practice problems.
Math.com
Math.com: Greatest Common Factor/practice Calculator
A page which generates number pairs and allows the user to find and enter the GCF. Keeps a running tally of correct/incorrect answers and has links to in depth review, if needed.
Math Is Fun
Math Is Fun: Prime Factorization
Find a definition or prime numbers and prime factorization, as well as examples on how to find the prime factors of 12 and 147. Also, follow a link to a Prime Factorization Tool.
PBS
Pbs Learning Media: Patterns of Factors
Demonstrate your grasp of patterns and factors by sorting the numbers into the correct columns. This interactive table focuses on factor pairs and prime factors for the numbers 2 to 36.
Calculator Soup
Calculator Soup: Prime Factorization Calculator
Use this prime numbers calculator to find all prime factors of a given integer number up to 1 trillion. This calculator presents prime factors of a number, prime decomposition in exponential form, CSV (comma separated values) list of...
Mathigon
Mathigon: Math Foundations: Divisibility and Prime: Greatest Common Factors
This lesson focuses on the greatest common factors it poses real situations and asks students answer them and then it provides more information and more exercises.
ABCya
Ab Cya: Prime Numbers
Number Ninja: Prime Numbers is a fast-action way to practice factors. Act quickly and use your finger or mouse to slice numbers and reduce them to their prime factors. Do not slice a prime number!
Khan Academy
Khan Academy: Prime Factorization
A practice quiz on the prime factorization of numbers. Includes hints.
Other
Help With Fractions: The Greatest Common Factor
Two different methods of finding the greatest common factor are explained at this one page website. It is very easy to follow the step by step directions.
Mangahigh
Mangahigh: Number: Prime Factoring
Explore prime factors and what the missing exponent could be.
Mathigon
Mathigon: Math Foundations: Divisibility and Primes: Prime Numbers
This lesson focuses on prime numbers, numbers that can only be divided by one and itself. It explains the Fundamental Theorem of Arithmetic and the Sieve of Eratosthenes. Includes practice activities.
Purple Math
Purplemath: Lcm & Gcf
Purplemath shows an easy and orderly way to determine the GCF and LCM of any two numbers. Even large numbers won't be a challenge with this method.
That Quiz
That Quiz: Factores
Interactive practice tests dealing with factors. Students will practice the prime factors, greatest common factor and least common multiple.
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...
Math Is Fun
Math Is Fun: Mathopolis: Practice Prime Factorization
A set of six multiple-choice questions practicing prime factorization. A help page is available for further study.
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...
Other
Greatest Common Factor/definition and Example
A walkthrough example of the discovery of the GCF of three numbers. Contains a definition as well.
Other
Greatest Common Factor/example
An example (with full explanation) where a Greatest Common Factor is found.
Scholastic
Scholastic: Study Jams! Math: Multiplication & Division: Prime Factorization
This site provides great practice on the concept of prime factorization. Students can first learn about the topic by watching a step by step instruction video that also points out areas of concern. Finally, students can practice their...