prime number

#include<stdio.h>
#include<math.h>
int main()
{int n, i,root,flag=0;
printf("enter a number: ");
scanf("%d",&n);
root=sqrt(n);
for(i=2;i<=root;i++)
{
    if(n%i==0)
    {
        flag=1;
        break;
    }
    else
    {
        flag =0;
        break;
    }
}

      if(flag==0)
      {
          printf("%d is a prime number",n);
      }
      else
      {
          printf("%d is not a prime number",n);
      }
      return 0;
        }