50 Fun Facts About Sudoku

In classic Sudoku, what size is the grid?

Each row, column and 3×3 box must contain every digit from 1 to 9 exactly once.

Under what name did the modern puzzle first appear in Dell Magazines in 1979?

Japan still generally calls it Number Place, or Nanpure for short, because Sudoku is a registered trademark there.

Which retired Indiana architect most likely designed the modern Sudoku?

He was 74 and freelancing as a puzzle constructor; he died in 1989, long before the craze.

How was Garns identified as the anonymous creator of the 1979 Dell puzzle?

New York Times crossword editor Will Shortz spotted the pattern.

Garns's colleagues at which Indianapolis firm recalled him drawing the puzzle at work?

A draftsman remembered him covering the grid up and saying it was "a game"; it was a secret.

Which Japanese puzzle company gave the puzzle the name Sudoku?

The company is named after a racehorse that won the Irish 2,000 Guineas in 1980.

What does the Japanese word Sudoku literally mean?

It is an abbreviation of a phrase meaning "the digits must be single", taking the first kanji of each word.

Which publisher and company president is known as "the father of Sudoku"?

He reportedly coined the shortened name while scrambling to get to a horse race.

What was the puzzle magazine Kaji launched in 1980 named after?

The horse won the 1980 2,000 Guineas in Ireland, and Kaji loved betting on the races.

What two innovations did the puzzle's Japanese publisher introduce in 1986?

Symmetrical means the givens sit in rotationally symmetric cells, a convention most setters still follow.

What was the profession of Wayne Gould, who spread Sudoku outside Japan?

He saw a partly finished puzzle in a Tokyo bookshop in 1997 and spent six years writing a program to generate them.

Which was the first newspaper outside Japan to print a Sudoku, in September 2004?

The New Hampshire paper beat The Times of London by two months.

What did Gould ask newspapers for in exchange for free puzzles?

His site sold a low-cost program, Pappocom Sudoku, that generated unlimited puzzles.

How did The Times of London spell the puzzle's name when it launched it in November 2004?

The first reader letter arrived the next day, from a man who had missed his tube stop because of it.

What did Ian Payn of Brentford complain about in the first Times letter on the puzzle?

Within months the puzzle had become a front-page feature in British national papers.

Who presented Sudoku Live, the world's first live TV Sudoku show, on Sky One in 2005?

Nine teams of nine players each solved cells on hand-held devices; the grand prize winner took over £23,000.

What was the BBC's 2005 game show combining Sudoku with general knowledge called?

It used only 4×4 and 6×6 grids and lasted four seasons.

Why was an Australian drugs trial costing over A$1 million aborted in 2008?

Four or five of the twelve jurors had been filling in grids instead of listening to the evidence.

What is the fewest clues a proper Sudoku can have?

A 2014 exhaustive computer search by McGuire, Tugemann and Civario proved no 16-clue puzzle exists.

Roughly how many completed 9×9 Sudoku solution grids exist?

Once rotations, reflections and relabellings are discounted, only 5,472,730,538 are essentially different.

A completed Sudoku grid is a special case of which mathematical object?

A Latin square only needs unique rows and columns; Sudoku adds the box constraint.

Which 18th-century mathematician inspired the name of that row-and-column array?

He used Latin letters as symbols; Korea's Choi Seok-jeong had published an order-nine example 67 years earlier.

Solving Sudoku on general n²×n² grids belongs to which complexity class?

Brute-force backtracking and dancing links still solve ordinary 9×9 puzzles quickly.

A Sudoku can be expressed as what kind of problem on a network of nodes and edges?

The aim is to complete a 9-colouring of a particular graph from a partial one.

Which Paris daily printed a partly filled 9×9 magic square with 3×3 subsquares in 1892?

It needed arithmetic rather than logic, so it was not quite a Sudoku.

What did the newspaper La France call its near-Sudoku puzzle of 1895?

These weekly puzzles ran in French papers for about a decade and vanished around World War I.

What name does the Japanese term Gattai 5 describe?

English-language papers such as The Times call the same layout Samurai Sudoku.

Which two puzzles does the Killer variant combine?

Cages outlined with dashes show a sum, and numbers cannot repeat within a cage.

In Killer Sudoku, what is the technique called that uses the total of any row, column or box?

A cell deduced inside the house is an "innie"; one outside is an "outie".

What is the Japanese name for Killer Sudoku, a Nipponised form of "sum num place"?

The Times introduced the variant to English speakers in 2005 and briefly confused everyone over whether cages could repeat digits.

What is another name for one of the nine 3×3 boxes in a Sudoku grid?

Three horizontally adjacent boxes form a band; three vertically adjacent ones form a stack.

How many groups (rows, columns and boxes combined) does a standard grid have?

The One Rule sums it up: each digit appears once in each group.

What is a 3-fish pattern called in Sudoku jargon?

An X-wing is the 2-fish, a jellyfish the 4-fish, and a squirmbag the rarely needed 5-fish.

What does a Sudoku solver mean by a "proper" puzzle?

A puzzle that needs no trial and error is called "satisfactory" instead.

What is a puzzle called if no clue can be removed without losing uniqueness?

Different minimal puzzles can have different numbers of clues.

What name does USA Today use for its 6×6 variant with 3×2 regions?

The Daily Mail runs a similar beginners' version called The Junior Sudoku.

What size is The Times' "Dodeka Sudoku"?

Dell's Number Place Challenger goes to 16×16, and Nikoli's Sudoku the Giant to 25×25.

What was the size of the "Sudoku-zilla" puzzle published in 2010?

Nikoli's 25×25 "Sudoku the Giant" looks modest by comparison.

What is The Times' three-dimensional Sudoku variant called?

The Daily Telegraph had published a 3D version as early as May 2005.

Which common variant requires the two main diagonals to contain unique digits too?

The Daily Mail's Sudoku X puzzles use 6×6 grids.

In "Clueless Sudoku", what forms the tenth puzzle?

Nine 9×9 grids sit in a 3×3 array, each with its middle cell left empty.

With which standard card game's 81-card deck can a tabletop Sudoku be played?

The deck's 81 cards map neatly onto the 81 cells of a grid.

Which organisation has run the Sudoku global championship since 2006?

The first event was held in Lucca, Italy; it skipped 2020 and 2021 for the pandemic.

Which Japanese solver has won the most individual world titles, with four?

Thomas Snyder of the US and Jan Mrozowski of Poland have three each.

Which country has won the most World Sudoku Championship team titles, with six?

China has five team titles and the Czech Republic three.

Where was the first World Sudoku Championship held in 2006?

Rounds have included a relay, where one puzzle's answer seeds the next, and a Guinness World Record speed round.

Roughly how many Sudoku apps were in Apple's App Store a fortnight after it opened?

The puzzle was already shipping on the Nintendo DS, PSP, Game Boy Advance and many Nokia phones.

Which AI lab used Sudoku as a reasoning benchmark for language models in 2025?

It partnered with the Cracking the Cryptic community to build the test bed.

Which magazine named Wayne Gould one of the world's most influential people in 2006?

His brother Bryan Gould was a British Labour politician.

Besides Sudoku, which loop-drawing puzzle did "the father of Sudoku" invent or introduce?

He resigned as head of Nikoli on 31 July 2021, ten days before his death.