Fatto generale: 5591 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 5591 is the smallest prime that is followed by 31 composite numbers.
Trivia: 5591 is a boring number.
Data storica: April 22nd is the day in 1912 that Pravda, the "voice" of the Communist Party of the Soviet Union, begins publication in Saint Petersburg.