Fatto generale: 16851 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 16851 is an uninteresting number.
Trivia: 16851 is a boring number.
Data storica: February 18th is the day in 1932 that the Empire of Japan declares Manzhouguo (the obsolete Chinese name for Manchuria) independent from the Republic of China.