Cube of 9
9 cubed equals 729. Cubes show up in volume calculations — a cube with side 9 holds 729 cubic units.
Cubes carry the fingerprint of their base. The final digit of 729 is 9 — always the cube of the base's own final digit. Divided by 9, a cube only ever leaves 0, 1 or 8, and 729 leaves 0. The volume picture explains the name: a 9 × 9 floor of unit cubes holds 81 of them, and 9 such layers stack to 729 — the shape itself is the exponent at work. The gaps grow like a parabola: 729 − 512 = 217, which is 3 × 9 × 8 + 1 — each new layer wider than the last. Odd base, odd cube: 729 stays odd, as 9 is.
| Expression | Value |
|---|---|
| 9³ | 729 |
Frequently asked questions
What is 9 cubed?
9 cubed is 729, because 9 × 9 × 9 = 729. The exponent 3 gives it the name "cube".
Why is it called a cube number?
Because it matches volume: a cube with side length 9 contains exactly 729 unit cubes.
Is 729 a perfect cube?
Yes — 729 = 9³, so it is a perfect cube by definition.