An integer (greater than one) is prime if the only whole numbers it can be divided by (without a remainder) are itself and one. All other integers are composite. In other words, a prime number has only two positive factors. Composite numbers have more. Fo
Eratosthenses was a Greek mathematician who figured out that to find all the prime numbers between two and some large number, you need to remove all the multiples of each number between two and your large number.
"A prime number is a positive integer that has exactly two positive integer factors, 1 and itself.
Fact Monster begins with a short prime number lesson, and a table of all the prime numbers between 1 and 1000.
For middle school and high school students, this Math Forum goes behind simple prime number definition, and introduces both Euclid's theory of prime numbers (which has been proven) and Goldbach's Conjecture (which hasn't.
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