Senary (base 6) is a number system that uses 6 digits (0, 1, 2, 3, 4 and 5). Examples are 12 in senary is 20 and 35 in senary is 55. And in senary, when it reaches 5, it will not be 6 because 6 is not in the senary system, so you add a 1 in front and 0 on everything else.[1][2]