Prime Clock
Number Theory
Level
3
Consider a digital 24-hour clock.
What is the first time after 12:00 noon when all the digits on the clock are prime numbers?
If your answer is 12:34, then enter it in as 1234.
The answer is 2222.
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1 solution
Least prime number is 2 . 24 hours clock either start with 1 or 2 . Since 1 is not a prime only time ≥ 2 0 could be prime. So the first prime time is 2 2 : 2 2