Асинхронный расчет факториала

using System;
using System.Diagnostics;
using System.Linq;
using System.Numerics;
using System.Threading.Tasks;

namespace AsyncFactorial
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                Console.WriteLine("Введите целое число:");
                int outNumber;
                if(int.TryParse(Console.ReadLine(), out outNumber))
                {
                    Stopwatch sw = new Stopwatch();
                    sw.Start();

                    Task<BigInteger> taskFact = new Task<BigInteger>(()=>FactEven(outNumber));
                    taskFact.Start();

                    Task<BigInteger> taskFact1 = new Task<BigInteger>(() => FactUnEven(outNumber));
                    taskFact1.Start();

                    BigInteger x = taskFact.Result * taskFact1.Result;

                    sw.Stop();
                    TimeSpan timeSpan = sw.Elapsed;

                    Console.WriteLine(timeSpan.ToString());
                    Console.WriteLine(Environment.NewLine);
                }
                else
                {
                    Console.WriteLine("Неверный вод числа");
                    continue;
                }
            }
        }

        static BigInteger FactEven(int numberFactorial)
        {
            BigInteger resultFact = 2;
            for(int i = 4; i <= numberFactorial; i += 2)
            {
                resultFact *= i;
            }
            return resultFact;
        }

        static BigInteger FactUnEven(int numberFactorial)
        {
            BigInteger resultFact = 1;
            for (int i = 3; i <= numberFactorial; i += 2)
            {
                resultFact *= i;
            }
            return resultFact;
        }
    }
}