Fatto generale: 7321 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 7321 is the number of intersections when all the diagonals of a regular 24-gon are drawn.
Trivia: 7321 is a boring number.
Data storica: January 16th is the day in 1707 that the Scottish Parliament ratifies the Act of Union, paving the way for the creation of Great Britain.