## Topic outline

• ### Playing With Numbers - Prime and Composite Numbers

• ### Prime and Composite Numbers

#### Prime Numbers

Let’s observe the factors of few natural numbers. We can see that number 1 has only one factor (i.e. itself).There are numbers that have exactly two factors i.e.1 and the number itself. Such numbers are 2, 3, 5, etc. These numbers are prime numbers. A number is called prime when it can't be divided evenly by any number except 1 or itself.

#### Therefore, Prime numbers are natural numbers that have only 2 factors i.e. 1 and itself.

Example: 19

19 have only two factors, 1 and 19. 19 cannot be divided evenly by numbers other than 1 or itself. So, 19 is a prime number.

#### The two numbers are said to be co-prime numbers when there is no number, other than 1, that divides both the two given number evenly. The HCF of these numbers should be 1.

Example: 6 and 35 are co-prime

#### Composite Numbers

Let’s observe factors of natural numbers again. There are numbers having more than two factors like 4, 6, etc. These numbers are composite numbers. When a number can be divided up evenly it is a Composite Number. A composite number has factors in addition to one and itself.

#### Therefore, numbers having more than two factors are called Composite numbers.

Example: 15

15 have three factors, 1, 5 and 15. 15 can be divided evenly by numbers other than 1 or itself. So, 15 is a composite number.

#### Prime and Composite Number Chart (1 to 100) #### 2. All the numbers in orange box are prime numbers. All the numbers in white box, other than 1 are composite numbers.

Important Notes:

#### 8. The sum two prime numbers can be even or odd.

• • • 