integer_expansion 0.0.0
1999.to_roman == 'MCMXCIX', 1999.to_old_roman == 'MDCCCCLXXXXVIIII', 4.! == 24, 1999.to_english == 'one thousand nine hundred and ninety nine', 1999.add_commas == '1,999'
1999.to_roman == 'MCMXCIX', 1999.to_old_roman == 'MDCCCCLXXXXVIIII', 4.! == 24, 1999.to_english == 'one thousand nine hundred and ninety nine', 1999.add_commas == '1,999'