My boy likes to think about numbers. Last night, he asked me "What comes after a zillion?". I didn't have an answer, so we looked it up on google and found that zillion is not a real number, but a slang word for "a really big number". The same page had a list of numbers multiplied by 1000. Thousand, Million, Billion, etc.
Jude wanted to write them all down in his journal for future reference.