Fatto matematico: 4647 is a member of the Fibonacci-type sequence starting with 1 and 7.
Trivia: 4647 is an uninteresting number.
Data storica: September 20th is the day in 1871 that Bishop John Coleridge Patteson is martyred on the island of Nukapu, a Polynesian outlier island now in the Temotu Province of the Solomon Islands.