AMHERST, Mass. — A Massachusetts college has changed all the speed limit signs on campus from 15 to 17 mph to honor a retired mathematics professor who spent his career fascinated by the number 17.

The change was made at the request of David Kelly, who didn’t want a retirement party when he stepped down last spring after 45 years on the faculty at Hampshire College in Amherst.

The change was backed by many on campus, including President Jonathan Lash.

Kelly knows countless facts about 17, the seventh prime number. He says it has had broad applications in mathematics and other disciplines. There are many fun facts about 17, including that there are 17 columns on the long side of the Parthenon in Greece.

Kelly says the tribute “captures Hampshire’s uniqueness.”