Factors are the numbers with which a given number is completely divisible. Let us consider an example, 12 is completely divisible by 1, 2, 3, 4, 6 and 12. So 1, 2, 3, 4, 6 and 12 are called the factors of 12. Counting the number of factors of 12, we come to know that there are 6 numbers by which 12 is completely divisible leaving no remainder. Thus, the number of factors of 12 is 6.
All Natural Numbers are divisible by 1 and itself. So every natural number has at least 2 factors. The natural numbers which have only 2 factors, 1 and itself are called Prime Numbers. Natural numbers that are not prime are called composite numbers. In short, composite numbers definition can be given, as the numbers which have 3 or more factors are called composite numbers.
If we consider an example then 8 is composite number because it is greater than 1 and it is not prime because it has the divisor 2, 4 and 8. But 7 is a prime number because it has only two divisor 7 itself and by 1.
In general we consider 1 as prime number because it divided by itself and 1 but when prime numbers were discovered at that time 1 is not considered to be a number that is why the scientist who discovered prime number doesn't consider 1 as a prime number. So, the number 1 is neither prime nor composite.
- 16 is divisible by 1, 2, 4, 8 and 16. So, it is a composite number.
- 4 is divisible by 1, 2, and 4. So, it is a composite number.
- 71 is divisible by only itself and 1. So, it is a prime number.
- 22 is divisible by 1, 2, and 11. So, it is a composite number.