C Program to Find whether a Number is Prime or Not using Recursion

The following C program, using recursion, finds whether the entered number is a prime number or not. A prime number is an integer that has no integral factor but itself and 1.

Here is the source code of the C program to find an element in a linked list. The C Program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
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 * C Program to find whether a Number is Prime or Not using Recursion

```
 */
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```
#include <stdio.h>
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```
 
```
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int primeno(int, int);
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int main()
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{
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    int num, check;
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    printf("Enter a number: ");
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    scanf("%d", &num);
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    check = primeno(num, num / 2);
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    if (check == 1)
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    {
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        printf("%d is a prime number\n", num);

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    }
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    else
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    {
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        printf("%d is not a prime number\n", num);

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    }
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    return 0;
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}
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```
 
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int primeno(int num, int i)
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{
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    if (i == 1)
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    {
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        return 1;
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    }
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    else
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    {
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       if (num % i == 0)
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       {
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         return 0;
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       }
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       else
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       {
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         return primeno(num, i - 1);
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       }       
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    }
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}
```

$ cc pgm24.c
$ a.out
Enter a number: 456
456 is not a prime number
 
$ a.out
Enter a number: 89
89 is a prime number

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