How to convert a number into words in C#

using System;

namespace NumberToWord

{

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("Pleas Enter the Number");

            int i = Convert.ToInt32(Console.ReadLine());

            string result = NumberToString(i);

            Console.WriteLine(result);

            Console.ReadLine();

        }

        public static string NumberToString(int num)

        {

            if (num == 0)

                return "zero";

            if (num < 0)

                return "minus " + NumberToString(Math.Abs(num));

            string words = "";

            if ((num / 1000000) > 0)

            {

                words += NumberToString(num / 1000000) + " million ";

                num %= 1000000;

            }

            if ((num / 1000) > 0)

            {

                words += NumberToString(num / 1000) + " thousand ";

                num %= 1000;

            }

            if ((num / 100) > 0)

            {

                words += NumberToString(num / 100) + " hundred ";

                num %= 100;

            }

            if (num > 0)

            {

                if (words != "")

                    words += "and ";

                var unitsMap = new[] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };

                var tensMap = new[] { "zero", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" };

                if (num < 20)

                    words += unitsMap[num];

                else

                {

                    words += tensMap[num / 10];

                    if ((num % 10) > 0)

                        words += "-" + unitsMap[num % 10];

                }

            }

            return words;

        }

    }

}

Output