General fact: 21296 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 21296 is an unremarkable number.
Trivia: 21296 is an unremarkable number.
Historical date: April 21st is the day in 1922 that the first Aggie Muster is held as a remembrance for fellow Texas A&M graduates who had died in the previous year.