19683

19683 is a number equal to (33)3 = 33 2 = 39 = 273. It can be written as \(3 \downarrow \downarrow 3\) in down-arrow notation, and therefore it shows up frequently when working with 3|threes in down-arrow notation, analogous to 7625597484987 in up-arrow notation.

With the fuga- prefix, this number can be named "fugathree".

19683's digits add up to its cube root: 1+9+6+8+3 = 27, and 273 = 19683. It is the largest number with that property.