Base-Twenty

A Base-Twenty or vigesimal number system is a counting method based on multiples of twenty. Many Native American tribes had base twenty systems, inspired by the total of twenty digits on the hands and toes. Base-twenty number systems are very easy to convert to and from base ten, because ten is a factor of twenty.

To convert from base-20 to base-10, multiply the number, minus the ones column, by two. Add the ones afterwards. Example: 21 &gt;&gt;&gt; (2*20)+1 &gt;&gt;&gt; 40+1 &gt;&gt;&gt; 41

To convert from base-10 to base-20, divide the number, minus the ones column, by two. Add the ones afterwards. Example: 82 &gt;&gt;&gt; (8*10)+2 &gt;&gt;&gt; (4*20)+2 &gt;&gt;&gt; 42