What is a prime number?
A prime is a whole number bigger than 1 that only divides by 1 and itself. 13 is prime. 15 is not, since 3 times 5 is 15. There are 8,363 primes with five digits, from 10007 to 99991.
How do you play?
- Type any five digit prime and press Enter.
- Green means the right digit in the right spot. Yellow means the digit is in the number but elsewhere. Grey means it is not.
- Find the hidden prime within six guesses.
How do you check that a guess is prime?
- It cannot end in 0, 2, 4, 5, 6 or 8, except for the primes 2 and 5 themselves.
- If its digits add up to a number that divides by 3, the whole number divides by 3, so it is not prime.
- If the game says your guess is not prime, try changing the last digit to 1, 3, 7 or 9.
What is a good strategy?
- Start with a prime that uses five different digits, so you test as many as you can.
- The last digit is always 1, 3, 7 or 9. Settle it early.
- Repeated digits are common in five digit primes, so do not rule them out.
- Keep a quick check list of small primes to divide by: 3, 7, 11 and 13 catch most fakes.
At a glance
| Tiles per guess | 5 |
| Guesses | 6 |
| Possible answers | 8,363 five digit primes |
| Daily puzzle | Yes, new at midnight UTC, plus Unlimited |
| Cost | Free, no account |
What do the answers usually look like?
Every five digit prime ends in 1, 3, 7 or 9. In our list the last digit splits like this: 7 (25%), 3 (25%), 9 (25%), 1 (25%). 70% of the primes repeat at least one digit, so do not rule out doubles.
A few answers from the pool, to show the style: 10007, 30803, 53017, 76207.