Prime Hunter
A grid of numbers hides a set of primes. Tap every prime, avoid the impostors like 51 and 91, and beat the clock. A daily grid is waiting.
How to play
- The grid holds numbers up to 99. Some are prime and the rest are composite.
- Tap every prime number. The clock starts on your first tap.
- A wrong tap is crossed out, counted as a mistake and shows the factors that prove it is not prime.
- Find every prime to finish. Your time and mistakes are shown at the end.
Tips and strategy
- Even numbers other than 2 are never prime, and neither are numbers ending in 5 other than 5 itself.
- Add the digits: if the total is a multiple of 3, the number is a multiple of 3, so it is not prime.
- Memorise the primes under 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.
- Watch the impostors: 51, 57, 87 and 91 look prime but are not (3 × 17, 3 × 19, 3 × 29 and 7 × 13).
FAQ
- Is 1 a prime number?
- No. A prime has exactly two divisors, 1 and itself, and 1 has only one. That is why 1 never appears in the grid.
- Is the daily grid the same for everyone?
- Yes. The daily grid is built from the UTC date, so everyone gets the same numbers and a new grid appears at 00:00 UTC.
- How many primes are hidden?
- About four in every ten tiles. The counter shows how many you have found out of the total.