Like the number of this clue (4)
(Other definitions for even that I've seen before include "Level, calm" , "Still - divisible by two" , "Still - flat" , "Equally balanced; level" , "Yet; level" .)
(Other definitions for prime that I've seen before include "Number such as two, three, five, seven, etc" , "Choice" , "Prepare to fire - first" , "At least two" , "Monastic service; best quality" .)