Function: Check Prime number or Not by using Function in C

Check Prime number or Not by using Function

#include<stdio.h>
#include<conio.h>
#include<math.h>
int main()
{
    int prime(int x);
    int n,flag;
    printf("Enter the number: ");
    scanf("%d",&n);
    flag=prime(n);
    if(flag==1)
printf("\n Yes!! %d is Prime number \n",n);
    else
printf("\n No!! %d is not Prime number \n",n);
    }
int prime(int x)
{
       int i,a;
a=sqrt(x);
       if((x==1)||(x==2))
 return(0);
       else
       {
    for(i=2;i<=a;i++)
if(x%i==0)
   return(0);
    return(1);
}
}