There is also one another interesting numbering systems:
the duodecimal (also known as dozenal), that is base 12.

We have good proves that this is how old Egyptians were counting.
They were using their thumb to count other finger joints (three in each of the four fingers, excluding the thumb), making it possible to count to 12.

In this base, the numbers are:

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ᘔ, Ɛ

And here is a multiplication table, where 100 means 144 (12×12):

That is – for instance – why we have:
– 2 x 12 hours a day
12 months a year
12 lunar cycles a year
– 12 zodiac signs
12 musical notes to the octave

etc.

There are also other things that come by twelve but that can hardly be linked to duodecimal, such as rainbow colors for instance…