using System;

using System.Linq;

using System.Collections;

using System.Collections.Generic;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        PrintNumber(1000);

        PrintNumber(10000);

        PrintNumber(Math.Pow(10.00001,4));

        PrintNumber(Math.Pow(10.00001,20));

        PrintNumber(Math.Pow(10.00001,21));

        PrintNumber(Math.Pow(10.00001,50));

    }

    private static void PrintNumber(double number){

        Console.WriteLine($"Global: {number.Format()} = {number.FormatChinese()}: Chinese");

    }

}

​

public static class NumberTools{

    public static string Format(this double value, bool decimals = false) {

        return FormattedText (value, ShortScales, decimals);

    }

    public static string FormatChinese(this double value, bool decimals = false) {

        return FormattedText (value, ShortScalesChinese, decimals, 4);

    }

​

    private static string FormattedText(double value, List<string> scales, bool decimals = false, int scalePower = 3)

    {

        if (decimals && value < Math.Pow(10, scalePower))

        {

            var digits = 1;

            for (; digits < scalePower; digits++)

            {

                if (value < Math.Pow(10, digits))

                    return value.ToString($"F{scalePower - digits}", CultureInfo.InvariantCulture);

            }

        }

        else if (value >= Math.Pow(10, scalePower))

        {

            var digits = value.CountDigits();

            var text = value.ToString("F0").Substring(0, scalePower);

            var left = digits % scalePower;

            if (left != 0) text = text.Insert(left, ".");

            else left = scalePower;

            var scale = digits - left;

            return text + scales[scale / scalePower - 1];

        }

        return value.ToString("F0");

    }

    private static int CountDigits(this double value)

    {

        return value >= 1 ? (int) System.Math.Floor(System.Math.Log10(value) + 1) : 0;

    }

    private static readonly List<string> ShortScales = new List<string> (new string[] {

        "k", //3

        "M", //6

        "B", //9

        "T", //12

        "q", //15

        "Q", //18

        "s", //21

        "S", //24

        "o", //27

        "N", //30

        "d", //33

        "U", //36

        "D", //39

        "Td", //42

        "qd", //45

        "Qd", //48

        "sd", //51

        "Sd", //54

        "Od", //57

        "Nd", //60

        "V", //63

        "Uv", //66

        "Dv",  //69

        "Tv",

        "qv",

        "Qv",

    });

    private static readonly List<string> ShortScalesChinese = new List<string> (new string[] {

        "万", //4

        "亿", //8

        "兆", //12

        "京", //16

        "垓", //20

        "秭", //24

        "穰", //28

        "沟", //30

        "涧", //34

        "正", //40

        "载", //44

        "极", //48

        "恒河沙", //52

        "阿僧祇", //56

        "那由他", //60

        "不可思议", //64

        "无量", //68

        "大数", //72

        "全仕祥", //76

    });

}

​