Ten is the basis for the primary number system adopted by most human civilisations, although often alongside other subsystems divisible by 3 and 4.

The decimal system has two main advantages. First it matches the number of digits on our hands. Second, its core unit values can be easily memorised. Most number systems larger than 16 use multiples of ten.

However, base 10 is not divisible exactly by 3, which plays a key role in geometry, but 1/3 may be rendered in decimal notation with recurring 3s, e.g. 0.333333˙.