There is not much need in America for a base-20 calculator... but if your culture uses both fingers & toes for counting - it will make learning math much easier!
In 1994 the students in Kaktovik Alaska created a number system for their language. It caught on fast and became the standard in the Iñupiaq culture. If you are unfamiliar with non-standard number bases (https://www.youtube.com/watch?v=EyS6FfczH0Q).
On the Apple App Store: https://apps.apple.com/us/app/kaktovik-calculator/id6468611124