NumberToWords converts an Int into English words

NumberToWords.scala

// NumberToWords converts an Int into English words

object NumberToWords extends App{

  val num2Word=Map((0, "Zero"), (1, "One"),
                  (2, "Two"), (3, "Three"),
                  (4, "Four"), (5, "Five"),
                  (6, "Six"), (7, "Seven"),
                  (8, "Eight"), (9, "Nine"),
                  (10, "Ten"), (11, "Eleven"),
                  (12, "Twelve"), (13, "Thirteen"),
                  (14, "Fourteen"), (15, "Fifteen"),
                  (16, "Sixteen"), (17, "Seventeen"),
                  (18, "Eighteen"), (19, "Nineteen"),
                  (20, "Twenty"), (30, "Thirty"),
                  (40, "Forty"), (50, "Fifty"),
                  (60, "Sixty"), (70, "Seventy"),
                  (80, "Eighty"), (90, "Ninety"),
                  (100, "Hundred"), (1000, "Thousand"),
                  (1000000, "Million"), (1000000000, "Billion")
  )


def bigNums(x: Int, limits: List[Int], stringBuilder: StringBuilder): Int={
  var i=x
  for {
    limit <- limits
  } {
    val units=i/limit
    if (units > 0 && units<1000){
      stringBuilder++=toWords(units)+" "+num2Word(limit)+" "
      i-=units*limit
      if (limit == 100 && i!=0) stringBuilder++="and "
    }
  }
  i
}

  def toWords(i: Int): String= {

    var x=i

    val out=new StringBuilder("")

    x=bigNums(x,List(1000000000,1000000,1000,100),out)

    if (x<100 && x>=20){
      val tens=x/10*10
      out++=num2Word(tens)+" "
      x-=tens
    }

    if (x<20) {
       if (x>0 || i==0)
        out++=num2Word(x)
    }

    out.toString()
  }

  println(toWords(0))
  println(toWords(1))
  println(toWords(20))
  println(toWords(70))
  println(toWords(71))
  println(toWords(111))
  println(toWords(8421))
  println(toWords(676123))
  println(toWords(923676123))
  println(toWords(1923676123))
  println(toWords(Int.MaxValue))
}

output.txt

Zero
One
Twenty 
Seventy 
Seventy One
One Hundred and Eleven
Eight Thousand Four Hundred and Twenty One
Six Hundred and Seventy Six Thousand One Hundred and Twenty Three
Nine Hundred and Twenty Three Million Six Hundred and Seventy Six Thousand One Hundred and Twenty Three
One Billion Nine Hundred and Twenty Three Million Six Hundred and Seventy Six Thousand One Hundred and Twenty Three
Two Billion One Hundred and Forty Seven Million Four Hundred and Eighty Three Thousand Six Hundred and Forty Seven