Scala ammonite script to turn a number into a a human readable(ish) representation, try ./num2word.sc 10002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001

num2word.sc

#!/usr/bin/env amm

@main
def main(n: BigInt): Unit =
  println(num2wordList(n, List.empty).mkString(" "))

// https://en.wikipedia.org/wiki/Names_of_large_numbers
private val prefix2factor = List(
    "Centillion" -> 303,
    "Googol" -> 100,
    "Vigintillion" -> 63,
    "Novemdecillion" -> 60,
    "Octodecillion" -> 57,
    "Septendecillion" -> 54,
    "Sexdecillion" -> 51,
    "Quindecillion" -> 48,
    "Quattuordecillion" -> 45,
    "Tredecillion" -> 42,
    "Duodecillion" -> 39,
    "Undecillion" -> 36,
    "Decillion" -> 33,
    "Nonillion" -> 30,
    "Octillion" -> 27,
    "Septillion" -> 24,
    "Sextillion" -> 21,
    "Quintillion" -> 18,
    "Quadrillion" -> 15,
    "Trillion" -> 12,
    "Billion" -> 9,
    "Million" -> 6,
    "Thousand" -> 3,
    "Hundred" -> 2
).map { case (prefix, base10) => prefix -> BigInt(10).pow(base10) }

private def num2wordList(n: BigInt, acc: List[String]): List[String] = {
  val found = prefix2factor.find { case (_, factor) => n >= factor }
  found match {
    case None =>
      if (n < 10L) singleDigit2word(n.toLong) :: acc
      else doubleDigit2wordList(n.toLong) ::: acc
    case Some((prefix, factor)) =>
      if (n % factor == 0) num2wordList(n / factor, prefix :: acc)
      else num2wordList(n / factor, prefix :: num2wordList(n % factor, List.empty) ::: acc)
  }
}

private def doubleDigit2wordList(n: Long): List[String] = {
  assert(n >= 10L && n < 100L)
  n match {
    case 10 => List("Ten")
    case 11 => List("Eleven")
    case 12 => List("Twelve")
    case 13 => List("Thirteen")
    case 14 => List("Fourteen")
    case 15 => List("Fifteen")
    case 16 => List("Sixteen")
    case 17 => List("Seventeen")
    case 18 => List("Eighteen")
    case 19 => List("Nineteen")
    case 20 => List("Twenty")
    case 30 => List("Thirty")
    case 40 => List("Forty")
    case 50 => List("Fifty")
    case 60 => List("Sixty")
    case 70 => List("Seventy")
    case 80 => List("Eighty")
    case 90 => List("Ninety")
    case _ => doubleDigit2wordList((n / 10) * 10) :+ singleDigit2word(n % 10)
  }
}

private def singleDigit2word(n: Long): String = {
  assert(n < 10L)
  n match {
    case 0 => "Zero"
    case 1 => "One"
    case 2 => "Two"
    case 3 => "Three"
    case 4 => "Four"
    case 5 => "Five"
    case 6 => "Six"
    case 7 => "Seven"
    case 8 => "Eight"
    case 9 => "Nine"
  }
}