Cube (algebra) however, easy to show that most numbers are not perfect cubes because "all" perfect cubes must have digital root 1, 8 or 9. That is their values modulo 9 may be only −1, 1 and 0. Moreover, the digital root of any number's cube can be determined by the remainder the number gives when divided by 3: Every positive integer can be written as the sum of nine (or fewer) positive cubes. This upper limit of nine cubes cannot be reduced because, for example, 23 cannot be written as the sum of fewer than nine positive cubes: The equation has
Dino Cube first mass-produced version had pictures of dinosaurs depicted on each piece, which led to the adoption of the puzzle's current name of "Dino Cube". It is not known what the puzzle had been called before this dinosaur version was introduced. The later versions, however, adopted the practice of using standard single-colour stickers, in common with most other twisty puzzles. The Dino Cube is a twisty puzzle in the shape of a cube. It consists of 12 movable pieces, all of which are located on the edges of the cube. The puzzle can be thought of as twisting around its corners: