sex-, sexi-, sext-
(Latin: six, sixth; a word element for number 6)
Don't confuse this sex- with another one that refers to "mating" or "gender".
sexennium
sexivalent
sexpartite
sexradiate
sextant
sextet
sextile
sextillion
sextillionth
sextodecimo
sextuple
sextupled
sextuples
sextuplet
sextuplicate