__Prime number__

- A
**prime number**(or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. - The property of being prime is called
**primality**

__Facts about Prime number__

**2**is the only prime number.- If the sum of the number’s digits is multiple of 3, that number can be divided by 3.
- No prime number greater than 5 ends with 5.
**0**and**1**are not considered prime numbers.- The largest known prime number (as of December 2020) is
**2^82,589,933 − 1**, a number that has**24,862,048**digits when written in base 10. It was found via a computer volunteered by Patrick Laroche of the**Great Internet Mersenne Prime Search (GIMPS)**in 2018.

__C program for checking Primality __

- #include<stdio.h>
- int main()
- {
- int num;
- int i;
- int m=0;
- int flag=0;
- printf("Enter a number to check prime or not\n");
- scanf("%d",&num);
- m = num/2;
- for(i = 2; i <= m;i++)
- {
- if(num%i == 0)
- {
- printf("Number is NOT prime\n");
- return 0;
- }
- }
- if(flag==0)
- printf("Number is prime\n");
- return 0;
- }

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