Fatto generale: 4878 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 4878 is the number of alternating knots with 13 crossings.
Trivia: 4878 is an uninteresting number.
Data storica: May 9th is the day in 1964 that Ngo Dinh Can, de facto ruler of central Vietnam under his brother President Ngo Dinh Diem before the family's toppling, is executed.