Uva Simply Emirp

#include<bits/stdc++.h>
using namespace std;
int arr[9999999]={0};
long int N=9999999;
void sieve()
{
    int sq=sqrt(N);
    arr[0]=1;
    arr[1]=1;
    arr[2]=0;
    for(long int i=4; i<N; i=i+2){
        arr[i]=1;
    }
    for( int i=3; i<=sq; i=i+2){
        if(arr[i]==0){
            for( int j=i*i; j<=N; j+=i)
            arr[j]=1;
        }
    }
}
int main()
{
    sieve();
   long int n;
    while(scanf("%ld",&n)==1){
   long int num=n;
    long int revers=0,mod;
    if(arr[n]==0){
            while(n!= 0){
        mod= n%10;
        revers= revers*10+mod;
       n/= 10;
    }
     if(arr[revers]==0 && revers!=num){
          printf("%ld is emirp.\n",num);
     }
     else
          printf("%ld is prime.\n",num);
    }
    else
         printf("%ld is not Prime.\n",num);
    }
    return 0;
}