General fact: 5551 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 5551 is the number of trees on 17 vertices with diameter 6.
Trivia: 5551 is a boring number.
Historical date: March 13th is the day in 1997 that the Phoenix lights are seen over Phoenix, Arizona by hundreds of people, and by millions on television.