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.

/*
* C Program to find whether a Number is Prime or Not using Recursion
*/
#include <stdio.h>

int primeno(int, int);

int main()
{
int num, check;
printf("Enter a number: ");
scanf("%d", &num);
check = primeno(num, num / 2);
if (check == 1)
{
printf("%d is a prime number\n", num);
}
else
{
printf("%d is not a prime number\n", num);
}
return 0;
}

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

$ 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