sexadecimal
/ˌsɛksəˈdɛsɪml/adjective
Relating to the number 16; specifically (of a number system) based on the number 16, rather than the usual 10; also as noun Compare sexdecimal.
Origin
Late 19th century; earliest use found in The Century Dictionary. Alteration of sexdecimal, either after sexa-, or with insertion of -a- after hexa-.