Distributive factorial in C#

gistfile1.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace ParallelFactorial
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var watch = System.Diagnostics.Stopwatch.StartNew();


            var result = await Factorial(1000);
         
            watch.Stop();
            var elapsedMs = watch.ElapsedMilliseconds;

            Console.WriteLine(elapsedMs);
            Console.WriteLine("Result = " + result);
            Console.ReadLine();
        }

        public async static Task<long> Factorial(int x)
        {
            int nr = x;

            var tasks = new List<Task<long>>();

            for (int i = 0; i < nr; i += (nr / 4))
            {
                int step = i;
                tasks.Add(Task.Run(() =>
                {
                    int right = (step + nr / 4) > nr ? nr : (step + nr / 4);
                    return ChunkFactorial(step + 1, right);
                }));
            }

           await Task.WhenAll(tasks.ToArray());


           return tasks.Select(t => t.Result).Aggregate(((i, next) => i * next));
        }

        public static long ChunkFactorial(int left, int right)
        {
            Console.WriteLine("ChunkFactorial Thread ID :" + Thread.CurrentThread.ManagedThreadId);

            if (left == right)
                return left == 0 ? 1 : left;
            else return right * ChunkFactorial(left, right - 1);
        }
    }
}