static void Main() { long targetNumber = 600851475143, factor = 1; string primeFactors = "1"; Problem3 prime = new Problem3(); for (long i = 2; i <= Math.Sqrt(targetNumber); i++) { if (targetNumber % ((2 * i) - 1) == 0) { factor = ((2 * i) - 1); if (prime.PrimeNumber(factor)) { primeFactors = primeFactors + " , " + factor.ToString(); } } } Console.WriteLine(primeFactors); Console.ReadKey(); }