A Hexavigesimal numeral system has a base of twenty-six.

Base 26 is a fairly natural way of representing numbers as text using the 26-letter Latin alphabet. The number of interest is expressed in base 26, and then the 26 different base-26 digits are identified with letters as 0=A, 1=B, 2=C, ... 25=Z.

This system is of limited practical value, although letters used in nominal or serial numbers can be thought as hexavigesimal numerals for calculation purposes if the entire alphabet is used.