UVA - 10235 - Simply Emirp

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        StringBuffer sb = new StringBuffer("");
        String m = "";
        boolean notPrime[] = sievePrime(1000 * 1000);
        while ((m = br.readLine()) != null) {
            int x = Integer.parseInt(m);
            if (notPrime[x]) {
                sb.append(x).append(" is not prime.\n");
            } else {
                int temp=reverse(x);
                if (notPrime[temp] || temp==x) {
                    sb.append(x).append(" is prime.\n");
                } else {
                    sb.append(x).append(" is emirp.\n");
                }
            }
        }
        System.out.print(sb);
    }

    static boolean[] sievePrime(int x) {
        boolean[] notPrime = new boolean[x + 1];
        notPrime[0] = true;
        notPrime[1] = true;
        for (int i = 2; i * i < x + 1; i++) {
            if (!notPrime[i]) {
                for (int j = i; i * j < x + 1; j++) {
                    notPrime[i * j] = true;
                }
            }
        }
        return notPrime;
    }

    static int reverse(int x) {
        StringBuilder sb = new StringBuilder(x + "");
        sb = sb.reverse();
        return Integer.parseInt(sb.toString());
    }
}