During his time at Princeton in the early 1960s, Kelly and fellow student
Michael Spivak created "
Yellow Pig's Day," an annual celebration of mathematics and the number 17. He continued to be involved in the organization of the holiday each year, commemorating the day with food, songs, a reunion, and mathematics. He was quite familiar with many of the properties of the number
17, and gave a special lecture on the subject each summer. ==Recognition==