Fatto generale: 5135 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 5135 is not the sum of a square, a cube, a 4^{th} power, and a 5^{th} power.
Trivia: 5135 is a boring number.
Data storica: January 21st is the day in 1958 that the last Fokker C.X in military service, the Finnish Air Force FK-111 target tower, crashes, killing the pilot and winch-operator.