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Check a number is a prime number or not by recursion

Programme:

#include<stdio.h>
 
int isPrime(int,int);
 
int main()
{
 
    int num,prime;
 
    printf("Enter a positive number: ");
    scanf("%d",&num);
 
    prime = isPrime(num,num/2);
 
    if(prime==1)
        printf("%d is a prime number",num);
    else
        printf("%d is not a prime number",num);
 
    return 0;
}
 
int isPrime(int num,int i)
{
    if(i==1)
    {
        return 1;
    }
    else
    {
       if(num%i==0)
            return 0;
       else
            isPrime(num,i-1);
    }
}

Output:

Enter a positive number: 17
17 is a prime number