Vigesimal

Vigesimal (also known as base 20) is a numeral system that uses 10 numbers and 10 letters (20 digits) : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, G, H, I, J and sometimes K. Vigesimal is related to Kaktovik numerals system, because they both use base 20. Sometimes, they do not use I because I looks like a 1. Examples are 3F is 75 (3 x 20 + 15 = 75) in decimal or 8H is 177 (8 x 20 + 17 = 177) in decimal. If you reach J or K, you put a 1 in front and 0 on everything else. Vigesimal is nearly double of decimal because 40 in vigesimal is 80 in decimal and this only works if the number is between 10-90 (only if they end with 0).^[1]

1. ↑ "Vigesimal Definition (Illustrated Mathematics Dictionary)". www.mathsisfun.com. Retrieved 2024-07-21.