Pertaining to, or founded on, the number sixty.

The sexagesimal (base-sixty) is a numeral system with sixty as the base. It originated with the ancient Sumerians in the 2000s BC, and was transmitted to the Babylonians. Sexagesimal as used in ancient Mesopotamia was not a pure base 60 system, in the sense that they didn't have 60 individual digits for their place-value notation.

of or relating to or reckoning in sixtieths; "the sexagesimal divisions of hours and degrees"

A sexagesimal fraction.

Base-60 numbering system.