When a number has more than 2 factors it’s called composite number. Number 8 is a composite number because it has more than 2 factors : 1, 2, 4, 8. How to calculate the composite number? For example, we take the number 10. To find the factors of 10, begin by dividing 1 by 10.

Step : 1 » 10 ÷ 1 = 10 [1 and 10 are factors of 10]
Step : 2 » 10 ÷ 2 = 5 [2 and 5 are also factors of 10]
Step : 3 » 10 ÷ 3 = 10 [Doesn’t divide evenly by 3, so 3 is not a factor of 10]
Step : 4 » 10 ÷ 4 = [Since 10 doesn’t divide evenly by 4, so 4 is not a factor of 10]
Step : 5 » 10 ÷ 5 = 2 [Here 5 and 2 are factors of 10]

We already know that 2 and 5 are also factors of 10, this 5 and 2 are repeat factors.

There is no need to repeat factors that we already know, in fact, while deriving the factors of number it’s important to understand that once we get repeat factors all other factors that we try will also repeat. Here dividing by anything greater than 5 will give us factors we already know, so we can stop here, so the factors of 10 are 1,2,5 and 10. When a number has more than 2 factors it’s called composite number.

Remember : 1 is not a prime number because it does not have exactly two different factors. 1 is not a composite number because it does not have more than 2 factors. So 1 is neither a prime nor a composite number.