How to play Prime Number Hunt
Prime Number Hunt fills a grid with numbers and asks you to claim every prime before the clock runs out. Once you have claimed a prime you can sieve with it, striking all of its multiples off the board at once — exactly how the Sieve of Eratosthenes works — so the fastest way through is to claim the small primes early and let them clear the ground.
For the boards that start above one hundred there are sieves for 2, 3, 5, 7, 11 and 13 you can use once each, at the cost of a few seconds. Claiming a number that is not prime costs a heart, and the game shows you why: 91 is 7 × 13.
There are four boards — 1 to 50, 1 to 100, 101 to 200 and 201 to 300 — and the later ones hold fewer primes hidden among composites with larger factors. Running out of time on a board costs a heart and shows the primes you missed.
Objective
Claim every prime on four number boards, using sieves to strike out the composites.
Features
- A playable Sieve of Eratosthenes on every board
- Small-prime sieves for the boards above one hundred
- Wrong claims explained with the number's factors
- Four boards from 1–50 up to 201–300
- Keyboard cursor or direct taps with a sieve switch
Keyboard
Touch
Scores are saved in this browser only. There is no global ranking and nothing is uploaded.