Bluebulb Projects' The Measure of Things presents:
21,000 is about twenty times the number of Population of Vatican City.
In other words, it's 24.90 times the count of Population of Vatican City, and the count of Population of Vatican City is 0.0402 times that amount.
(a.k.a. Vatican City State, a.k.a. Stato della Città del Vaticano
, a.k.a. Status Civitatis Vaticanae
) (Rome, Italy) (2014 estimates; permanent residents only)