Factors and Primes

Students learn that a factor of a number divides into the number without a remainder. For example, 7 is a factor of 14, because 7 divides into 14 without a remainder. To find the factors of a number, such as 8, first divide 8 by 1, which equals 8. Since there is no remainder, both 1 and 8 are factors of 8. Next, divide 8 by 2, which equals 4. Since there is no remainder, both 2 and 4 are factors of 8. Next, divide 8 by 3. Since 8 is not divisible by 3, then 3 is not a factor of 8. Next, divide 8 by 4, which equals 2. Since there is no remainder, both 4 and 2 are factors of 8. Notice, however, that 4 and 2 are repeat factors (we already know that 4 and 2 are factors of 8). This means that all other factors will also be repeat factors, so there is no need to continue -- the factors of 8 are 1, 2, 4, and 8. Note that a number that has more than two factors, such as 8, is called a composite number, and a number that has only two factors (itself and 1), such as 5, is called a prime number.

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