How to Do Cube Roots of 9 Digit Numbers in Your HeadWhat is a Cube Root? (Just in case you don't already know.) A number cubed is that number times itself times itself. For example, 4 cubed, normally written 43, is 4 × 4 × 4 = 64. The cube root goes in the opposite direction, so the cube root of 64 is 4. To give a larger example, 657 cubed = 6573 = 657 × 657 × 657 = 283593393, so the cube root of 283593393 is 657. Doing it in your head Now
