How do you figure out simplest radical form with variables and/or exponents and/or numbers outside the square root

Answer 1

if taking nth roots, look for nth powers and take them out of the radical, since the nth-root of x^n = x

example:
√300 = √100√3 = 10√3

∛640 = ∛64∛10 = 4∛10

∜80 = ∜16∜5 = 2∜5

Answer 2

What is the 9th root of 64, in simplest radical form?