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# Prime Numbers

Numbers starting with 1, 2, 3, 4.…… are called Natural Numbers. Natural numbers are denoted by ‘N’. These numbers are put into different groups. The group may be of Even Numbers, odd numbers, Prime Numbers or even composite numbers.

A number which is divided by itself and by 1 is called a prime number. Prime number can also be defined as the Odd Numbers which are not divided by any odd number except 1 and itself. Prime numbers are mainly 1, 2, 3, 5, 7, and 11 and so on.

Prime numbers are always greater than 1 and don't have any divisor except 1 and itself. As we know that prime numbers are always positive but the number which are greater than 1 and it is also not prime then this type of number are called as Composite Number.

If we take an example then 7 is a prime number because it has only two divisor 7 itself and by 1. And 8 is composite number because it is greater than 1 and it is not prime because it has the divisor 2, 4 and 8.

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.

But in the first factor we haven't included 1, and we know that by the definition of prime number the number should be divisible by 1 and itself. So whenever we say that 1 is not a prime number then we have to change our definition, if we are considering a number divisible by 1 to be a prime number then 1 should be a prime number.

Examples:
1. 5 is divisible by only itself and 1. So, it is a prime number.
2. 16 is divisible by 1, 2, 4, 8 and 16. So, it is a composite number.
3. 71 is divisible by only itself and 1. So, it is a prime number.
4. 13 is divisible by only itself and 1. So, it is a prime number.

## History of Prime Numbers

A number which is divided by itself and by 1 is called a prime number. Prime number can also be defined as the Odd Numbers which are not divided by any odd number except 1 and itself. Prime numbers are always greater than 1 and don't have any divisor except 1 and itself. Prime numbers are mainly 1, 2, 3, 5, 7, and 11 and so on.