Summary and Practice Exercise
Summary
In the previous pages, we have learned that a number can be expressed as a product of two numbers which we call factors. For example, in the multiplication sentence 2 x 3 = 6, 6 is the product and 2 and 3 are factors. The expression 2 x 3 is a factorization of 6.
We also learned that there are numbers with only two factors (or one factorization). For example, the number 7 has only 1 and 7 as factors (or only 1 x 7 as factorization). These numbers are called prime numbers. Since the factors are also divisors of the number, another way to think about a prime number is that it is a number that has only two divisors, 1 and itself.
Numbers with more than two factors (or divisors) are called composite numbers. For example, the number 6 can be factorized as 1 x 6 and 2 x 3, which means that it has 4 factors. These are 1, 2, 3, and 6.
Also, the number 1 is a special number. It is not composite and it is not prime.
Practice Exercise
Classify the numbers as prime or composite. Use the red button to drag the numbers inside the appropriate rectangle.