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# Prime Numbers

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Numbers starting with 1, 2, 3, 4.ā¦ā¦ are called Natural Numbers. Natural numbers are denoted by āNā. 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.