Not sure how elegant this is, but here is my number-to-its-English-word-counterpart translator

englishnumber.rb

def numwords any_number
  bignumwords any_number, []
end

def bignumwords number, big_array
	place_names = {1 => 'thousand', 
                 2 => 'million', 
                 3 => 'billion', 
                 4 => 'trillion'}
	comma_count = Math.log(number,10).floor / 3
	comma_count.downto(1) do |commas|
		leading_digits = number / (10**(commas*3))
		big_array << smallnumwords(leading_digits)
		big_array << place_names[commas]
		number = number % (10**(commas*3))
	end
	big_array << smallnumwords(number)
	big_array.join(' ')
end

def smallnumwords smallnumber
	words_under_a_hundred smallnumber, []
end

def words_under_a_hundred input_number, the_word_array
	num_names = {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'}
	
	if input_number == 0
		return the_word_array.join(' ')
	elsif input_number >= 100
		the_word_array << num_names[input_number/100]
		the_word_array << 'hundred'
		input_number = input_number % 100
		words_under_a_hundred(input_number, the_word_array)
	elsif input_number >=20
		the_word_array << num_names[(input_number/10)*10]
		if input_number%10 != 0
			the_word_array << num_names[(input_number%10)]
		end
	else
		the_word_array << num_names[(input_number)]
	end
	
	the_word_array.join(' ')
end

puts numwords(3231234151)
puts numwords(1515181)
puts numwords(30845)
puts numwords(100)
puts numwords(3)