**A. Factors are the numbers that are multiplied to give a product.**

5×4 = 20

5 and 4 are factors of 20.

factors of number also divide that number without leaving any remainder.

24÷3 = 8 (8 and 3 are both factors of 24.)

**B. When you multiply a number by 1,2,3,4, …, the products are all multiples of the number.**

For example, 3, 6, 9, 12, are all multiples of 3, as (3×1), (3×2), (3×3), (3×4).

**C. Rules of Divisibility**

The rules of divisibility will help you find which numbers divide others without leaving any remainder.

**A number is divisible by**

**If the last digit is**

**A number is divisible by**

**If the Sum of the digits is divisible by**

**D. Prime Numbers and Composite Numbers**

The numbers 2, 3, 5, 7, …, have only two factors each – the number itself and the numbers 1. Such numbers are called prime numbers.

*A prime number is any number greater than 1 that has only two factors – the number itself and the number 1.*

6 has 4 factors. They are 1, 2, 3, and 6.

6 is called a composite number.

*A composite number is any number greater than 1 that has more than different factors.*

**1 is a special number. It is neither prime nor composite.**