Prime and Composite numbers

A prime number is one that has precisely two factors; this means, it can just be divided by number 1 and itself. One important thing to remember is that 1 is not a prime number. Example of the prime number-

7 is said to be the prime number as the only factor that would equal 7 is 1*7.

Next example is of 3 as it can only be divided by two numbers, i.e. 1 and 3-
3/1= 3
3/3= 1

Few other prime numbers are 2, 5, 11, 13 and 17.

They are the whole numbers which have more than two factors. This implies that except for getting divided by number 1 or themselves. They can be also be divided by one integer or number. An important thing to note is 1 is not a composite number. Examples of composite number-

8 is said to be a composite number as it has more than two factors that when multiplied together will equal 8, 1*8 and 2*4 both equal 8

Another example is 12=
12/1= 12
12/2= 6
12/3= 4
12/4= 3

(See What is 1/4 plus 1/4?)

This list would help you in identifying both the prime and composite numbers. The prime numbers are in red and composite numbers are in blue-

It is imperative for you to know that 2 is the smallest prime number, and 4 is the smallest composite number. Also, 0 and 1 are neither prime nor a composite number. The next important thing is that all the even number can be divided by 2; therefore all even numbers which are greater than 2 are composite numbers.

Also, all the numbers greater than 5 are divisible by 5. Hence all numbers greater than 5 are composite numbers. (See What is pi? What is the meaning of Pi?)