It’s interesting to note (no pun intended) that the most numerous U.S. currency note in circulation is the $100, not the $1, note. Although the $1 note is perhaps the most numerous within the U.S., around the world–in which the principal reserve currency in international trade is U.S. , the $100 note is the most popular and numerous. There are 1.43 billion $1 notes in circulation worldwide, but there are 18.5 billion $100 notes ($1.85 trillion). That’s equal to 2.3 $100 notes for every man, woman, and child on Earth.