General fact: 15818 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 15818 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 15818 is an uninteresting number.
Historical date: April 22nd is the day in 1930 that the United Kingdom, Japan and the United States sign the London Naval Treaty regulating submarine warfare and limiting shipbuilding.