Euclid around 300 BC stated that Prime numbers are more than any assigned quantity of prime numbers.

According to Euclid there are infinite prime numbers.

Prime numbers are like siblings, although members of the same big family resembling each other, but not quite alike.

Which is the oddest of all prime numbers? It is 2 mainly because it is the only even prime number.

The number 1 has only one positive divisor and that is one itself.
Every number (a), where a>1, would have at least two positive divisors, ‘1’ and ‘a’
A number "a > 1" is called a prime number or we simply call it prime if it has only two positive divisors.

A prime number is a whole number larger than the number 1 and one that can be equally divided only by itself and 1.
All prime numbers beyond 2 are considered odd because all even numbers can be divided evenly by 1 themselves and by 2.
So even numbers larger than 2 won’t fit into the definition of a prime number.
Since prime numbers are not formed by multiplying any two or more numbers they cannot be divided by any number.

Prime number definition: A prime number is a positive integer which has only two factors, which can be 1 and the number itself.

For example, lets consider the number 2.

2 = 2 × 1

So, 2 has factors 2 and 1. It means it has only two numbers as factors. Hence it is a prime number.

Now, lets consider the number 6.

6 = 3 × 2

= 3 × 1 × 2 × 1

= 3 × 2 × 1

6 has three factors 3, 2 and 1. So it is not a prime number.

Such numbers are called composite numbers.

The first few prime numbers are: 2 , 3 , 5 , 7 . ...............

There are various methods to find out what are prime number, they are:

1. Sieve of Eratosthenes

This provides a method to test a number to see if it is prime.

The method is as follows:
Write the list of numbers starting from 2 and going up to any limit, say 15 .

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

The first prime number is 2. Circle 2 and cross out all the multiples of 2
Prime Number 2
The next unmarked number is 3 , so circle it and cross out all of its multiple.
Prime Number 3
Next, its 5 . Circle it and cross out all of its multiple.
Prime Number 5
Similarly we do it up to 19.
Prime Number 7, 11 and 13
Taking all the circled numbers,

2 , 3 , 5 , 7 , 11 and 13

We get the list of first prime numbers, up to 15 .

2. Another method for determining whether a number is prime is to divide the number by all primes less than or equal to the square root of that number. If any one primes of the divisions forms an integer, then the original number is not a prime. Otherwise, it is a prime.