Convert Rupees (Numbers) to Words (String) using C#.NET

public string ConvertNumbertoWords(long number)
{
    if (number == 0) return "ZERO";
    if (number < 0) return "minus " + ConvertNumbertoWords(Math.Abs(number));
    string words = "";
    if ((number / 1000000) > 0)
    {
        words += ConvertNumbertoWords(number / 100000) + " LAKES ";
        number %= 1000000;
    }
    if ((number / 1000) > 0)
    {
        words += ConvertNumbertoWords(number / 1000) + " THOUSAND ";
        number %= 1000;
    }
    if ((number / 100) > 0)
    {
        words += ConvertNumbertoWords(number / 100) + " HUNDRED ";
        number %= 100;
    }
    //if ((number / 10) > 0)
    //{
    // words += ConvertNumbertoWords(number / 10) + " RUPEES ";
    // number %= 10;
    //}
    if (number > 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 (number < 20) words += unitsMap[number];
        else
        {
            words += tensMap[number / 10];
            if ((number % 10) > 0) words += " " + unitsMap[number % 10];
        }
    }
    return words;
}