Calculator Soup
Calculator Soup: Prime Number Calculator
This prime number calculator will find if a number is prime or composite. If it is composite the calculator will also find all of the factors of the composite number.
University of Waterloo (Canada)
Wired Math: Primes and Prime Factors [Pdf]
Explore primes, prime factors, and composites using this collection of worksheets. Lots of detailed examples, interesting math facts, and colorful visuals. Acrobat Reader required.
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.
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.
E-learning for Kids
E Learning for Kids: Math: Amazon River Boat Trip: Multiplication and Division
Explore prime and composite numbers, multiplication, and division with Julie throughout these interactive exercises.
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.
Cuemath
Cuemath: Prime Numbers
Learn about the history of prime numbers, properties of prime numbers, and easy methods to find prime numbers. Included are solved examples and interactive problems for review.
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...
Mocomi & Anibrain Digital Technologies
Mocomi: What Is a Prime Number?
Explains prime numbers and gives examples.
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.
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...
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.
E-learning for Kids
E Learning for Kids: Math: Inca Temple: Number Sense
Do you want to know how to pronounce really big numbers? Paul can teach you!
ClassFlow
Class Flow: Number Sense Related to Division
[Free Registration/Login Required] This flipchart introduces divisibility, primes and composites, averages, and estimating quotients.
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."
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.
National Institute of Educational Technologies and Teacher Training (Spain)
Ministerio De Educacion: Divisores Y Primos
Reinforce your knowledge on prime numbers and their divisors.
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...
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...