List<long> digits = new List<long>();
            for (long i = 1000; i <= 9999; i++)
            {
                int counter = 0;
                long number = i;
                foreach (long x in primes)
                {

                    if (number % x == 0)
                    {
                        number = number / x;
                        counter++;
                    }
                    if (counter == 4)
                        digits.Add(i);
                }
            }