Hecho general: 21753 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 21753 is an uninteresting number.
Trivia: 21753 is an unremarkable number.
Fecha histórica: July 22nd is the day in 1933 that Wiley Post becomes the first person to fly solo around the world traveling 15,596 miles (25,099 km) in 7 days, 18 hours and 45 minutes.