Mathematical fact: 591 is the number of ways to stack 23 boxes in a line so that each box lies on the table or on a box next to 2 boxes.
Trivia: 591 is an uninteresting number.
Historical date: August 13th is the day in 1969 that the Apollo 11 astronauts are released from a three-week quarantine to enjoy a ticker-tape parade in New York.