I am assuming that you mistyped and meant to write 729-1/3. Written in radical notation it would be: -1√(729/3) = -1√243, (this is taking into account that a regular square root can be written as 2√X and a cube root would be 3√X). However, with roots, one can write the equation √4 as (4)^(1/2) which both would be equal to 2. So with the number you have written, it can be re-written as (729/3)^-1 which would be the same as 3/729.
If you just accidentally wrote the "-" and the actual question is just (729^1)/3 then the answer would purely be 729/3 which is equal to 243.