private static void initFactors() {
        Arrays.fill(factors, 0, MAX, 1);

        int x= (int) Math.sqrt(MAX);

        for (int i = 2; i<=x ; i++) {

            for (int j = i; j < MAX; j += i) {

                if ((j%i)==0)
                    factors[j]++;
            }
        }
    }