As mentioned above, the Mayan number system is base-20. They also invented the concept of zero, apparently before anyone else on Earth did, in order to have a positional number system. Also the first of its kind.

A positional number system makes it possible to write very large numbers (billions, trillions) which they did, and to do arithmetic with such large numbers. (Try doing arithmetic with Roman numerals and you see the problem right away.)

This enabled the Mayans to take nightly measurements of the positions of stars and planets using Stone Age instruments (no telescopes) yet end up with extremely accurate results. They did this by averaging thousands of measurements to eliminate the noise from the data. (A technique re-invented by and credited to Gauss). By this method, they computed the orbital behavior of Venus to an astounding degree of accuracy only exceeded in the second half of the 20th century.

I wonder if base-20 number systems, especially with a sub-base of five, show up in other parts of the Americas, too.

@shuttersparks
> "I wonder if base-20 number systems, especially with a sub-base of five, show up in other parts of the Americas, too."

Well, I just read this article not too long ago: https://www.scientificamerican.com/article/a-number-system-invented-by-inuit-schoolchildren-will-make-its-silicon-valley-debut/

But this is a base-20 number system invented very recently (in living memory) by First Nations peoples of Canada. It is notable in how the geometric construction of the numerals make it easy to do mental math by performing simple translations and rotations on parts of the numbers.

@ramin_hal9001 Yes, I posed the question in a post that was a comment in a thread about the numeral system developed by Inuit schoolkids.