Definitions
In mathematics, additive primes are prime numbers for which the sum of their decimal digits are also primes.



Task
Write a program to determine (and show here) all additive primes less than 500.

Optionally, show the number of additive primes.



Also see

   the OEIS entry:   A046704 additive primes.
   the prime-numbers entry:   additive primes.
   the geeks for geeks entry: additive prime number.
   the prime-numbers fandom: additive primes.


public class additivePrimes {
 
    public static void main(String[] args) {
        int additive_primes = 0;
        for (int i = 2; i < 500; i++) {
            if(isPrime(i) && isPrime(digitSum(i))){
                additive_primes++;
                System.out.print(i + " ");
            }
        }
        System.out.print("\nFound " + additive_primes + " additive primes less than 500");
    }
 
    static boolean isPrime(int n) {
        int counter = 1;
        if (n < 2 || (n != 2 && n % 2 == 0) || (n != 3 && n % 3 == 0)) {
            return false;
        }
        while (counter * 6 - 1 <= Math.sqrt(n)) {
            if (n % (counter * 6 - 1) == 0 || n % (counter * 6 + 1) == 0) {
                return false;
            } else {
                counter++;
            }
        }
        return true;
    }
 
    static int digitSum(int n) {
        int sum = 0;
        while (n > 0) {
            sum += n % 10;
            n /= 10;
        }
        return sum;
    }
}
 