The simplest radical form of √64 is 8.
To explain, the square root of a number is a value that, when multiplied by itself, gives the original number. For 64, we want to find a number that fulfills this condition.
64 is a perfect square because it can be expressed as 8 × 8. Therefore, the square root of 64 is simply 8. Since 8 is already a whole number, we say that 8 is the simplest radical form of √64.