# Prime Number Program In C

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Any whole number which is greater than 1 and has only two factors that is 1 and the number itself, is called a prime number. Other than these two number it has no positive divisor. For example −

```7 = 1 × 7
```

Few prime number are − 1, 2, 3, 5 , 7, 11 etc.

## Algorithm

Algorithm of this program is very easy −

```START
Step 1 → Take integer variable A
Step 2 → Divide the variable A with (A-1 to 2)
Step 3 → If A is divisible by any value (A-1 to 2) it is not prime
Step 4 → Else it is prime
STOP
```

## Pseudocode

We can draft a pseudocode of the above algorithm as follows −

```procedure prime_number : number

FOR loop = 2 to number - 1
check if number is divisible by loop

IF divisible
RETURN "NOT PRIME"
END IF

END FOR

RETURN "PRIME"

end procedure
```

## Implementation

Implementation of this algorithm is given below −

```#include <stdio.h>

int main() {
int loop, number;
int prime = 1;

number = 11;

for(loop = 2; loop < number; loop++) {
if((number % loop) == 0) {
prime = 0;
}
}

if (prime == 1)
printf("%d is prime number.", number);
else
printf("%d is not a prime number.", number);
return 0;
}
```

## Output

Output of the program should be −

```11 is prime number.
```
mathematical_programs_in_c.htm