Fatto matematico: 4900 is the only non-trivial number which is both square and square pyramidal.
Trivia: 4900 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: May 31st is the day in 1991 that Bicesse Accords in Angola lay out a transition to multi-party democracy under the supervision of the United Nations' UNAVEM II mission.