NumbersGrid

NumbersGrid takes the row-and-column grid of sports and geography dailies and fills it with number theory. The rows and columns name properties a whole number can have, and each of the nine squares wants one number that has both of its properties. Tap a square, type a positive number and press Prove It: the game tests the number against both properties as you enter it, rather than checking it against a list of answers, so any number that really fits is accepted.

No number may be used twice, and the score depends on the number you choose, not only on whether it fits. Answers are ranked by how deep in the sequence they sit, from Common at 100 points through Not Bad and Lovely to Mathematician at 1000. On 21 October 2026 the columns were Kaprekar Number, High Multiplicative Persistence and Coprime to Thirty, and the rows Sum of Two Squares, Palindromic Square and Odious Number; 13 in the coprime and sum-of-two-squares square counted as Common.

The 87 properties come in five families: digit patterns, divisors, figurate forms such as triangular and square numbers, primes, and remainders. A Current Classifications page explains each one, and today's grid is drawn from them by a shuffle seeded with the date. A practice mode deals random grids as often as you like, a streak counts the days you finish, and a finished grid can be copied as a result to share.

It runs in the browser with no account and no ads, in a pixel style with small sounds and number facts that pop up in the background. It suits players who like numbers for their own sake and know that 6174 or 1729 has a name.