Converting numbers to English text

NumberText1.scala

object NumberText1 {

    val u = Map(
        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"
    )
    val t = Map(
        2 -> "twenty", 3 -> "thirty", 4 -> "forty", 5 -> "fifty",
        6 -> "sixty", 7 -> "seventy", 8 -> "eighty", 9 -> "ninety"
    )
    val someAnd = Some("and")

    def conv(n: Int) = {
        def conv(n: Int, units: String*): List[Option[String]] = {
            if (n > 0) {
                val mod = n % 1000
                val div = mod / 100
                val rem = mod % 100

                val and = if (div > 0 && rem > 0) someAnd else None
                val tens = if (rem < 20) List(u.get(rem)) else List(t.get(rem / 10), u.get(rem % 10))
                val triplet = u.get(div).map(h ⇒ h + " hundred") :: and :: tens
                val unit = if (mod > 0) Some(units.head) else None

                conv(n / 1000, units.tail: _*) ::: (triplet :+ unit)
            } else List(None)
        }

        if (n > 0) {
            val div = conv((n / 1000) * 1000, "", "thousand", "million", "billion")
            val and = List(if (n > 1000 && n % 1000 < 99 && n % 100 > 0) someAnd else None)
            val mod = conv(n % 1000, "")
            (div ::: and ::: mod).flatten.mkString(" ")
        } else "zero"
    }

    def main(args: Array[String]): Unit = {
        (1 to 100).map(conv).foreach(println)
        println(conv(10101010))
        println(conv(909090909))
        println(conv(1314159265))
        println(conv(324872004))
    }

}