General fact: 21228 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 21228 is an uninteresting number.
Trivia: 21228 is a boring number.
Historical date: February 12th is the day in 2002 that an Iran Air Tours Tupolev Tu-154 crashes in the mountains outside Khorramabad, Iran while descending for a landing at Khorramabad Airport, killing 119.