Barrett connected five times from 3-point range for the Tigers (6-7), who were 6-for-8 behind the arc in the first half and led 41-32 at the break.
Hummer scored 16 first-half points, and the senior forward moved into seventh place on Princeton's career scoring list with 1,381, passing Bob Scrabis (1985-89). Hummer made 10 of 16 shots in the game.
Jack Isenbarger scored 16 points and Lucas Troutman 14 to pace Elon (8-6), which never led. The Phoenix won 56-55 at Princeton last season and had beaten their two previous Ivy League opponents this season, Dartmouth and Columbia.
Isenbarger made two 3-pointers to move into a tie for fifth with Chris Long (2007-11) on Elon's career list with 172.
Officials: North Carolina must show proof of discrimination-free zone, or lose NCAA tournament games
North Carolina must prove to the NCAA that its host arenas will provide a discrimination-free zone, or risk losing NCAA tournament games in 2017 and 2018, multiple officials told ESPN.
Jalen Rose and David Jacoby examine the new NCAA draft rule and consider how it would have affected "The Fab Five."
Florida and Duke will meet on Dec. 6 in the Jimmy V Classic at Madison Square Garden as one of two high-profile games to help raise funds for cancer research.