Binary Fingers!
www.mathsisfun.com
Forget about counting to 10 on your fingers ... you can count past 1,000 if you want! With just your right hand you can count to 31:

cross-posted from: https://sh.itjust.works/post/53581443

YSK You can count past 1,000 on your fingers by using binary, instead of just 10

With just one hand, you can count to 31, and with both hands you can reach a whopping 1,023. This is because the placement of the held up fingers matters, rather than the amount.

It can be very useful in everyday use, being able to count to huge numbers when you don’t have your phone or pen and paper nearby.