How rare is a $100,000 bill?

I'm curious, just how scarce is a $100,000 bill? It's not something I've ever come across in my daily life, so I'm wondering if it's something incredibly unique or if there's a certain reason it's not commonly used. Are these bills still in circulation, or were they discontinued long ago? I'm fascinated by the rarity and history behind such a high denomination, and I'd love to hear more about it.