Did you know?
The number of ways to fill a 9 × 9 sudoku grid has 22 digits! It is about 6,670 million million million. Even if you solved one every second for your whole life, you would never run out.
India has hosted the World Sudoku Championship twice: in Goa in 2008 and in Bengaluru in 2017. The very first championship was held in Lucca, Italy, in 2006.
KenKen, a cousin of sudoku, was invented in 2004 by Tetsuya Miyamoto, a maths teacher in Japan. Its name comes from a Japanese word for cleverness. In KenKen, you also add, subtract, multiply or divide!
Try this: Mini Sudoku Challenge
Copy this 4 × 4 grid. Fill in 1, 2, 3 and 4 so that each number appears once in every row, every column and every 2 × 2 corner box. Tip: start with the top-right box.
| 3 | 2 | ||
| 4 | |||
| 3 | 4 | ||
| 4 |
Show answer
row by row: 4132, 2314, 3421, 1243
Go further: Sudoku with Sums
In killer sudoku, the grid is split into dotted shapes called cages. Each cage shows a small number: the numbers inside it must add up to that total, with no number repeated in the cage. The usual sudoku rules still apply. Some killer sudokus begin with no numbers at all, only cages! Try this: in a 4 × 4 killer sudoku, a cage of two squares adds up to 3. Which two numbers must go there? (1 and 2!)