13.
In DBZ when you go into the spirit world your body doesn't age.
Also, fun fact, a googolplex (10^(10^100)) is so big that if you got the entire observable volume of the universe, packed it full of dust particles 1.5 micrometres apart, then gave each particle a number (like 1, 2, 3, 4, 5, ... etc) and then counted all the different arrangements those particles could be placed in. That would be approximately a googolplex.