Excluding the numbers 2 and 5, every prime number must end in one of which four digits in a base-10 system?
Show answer
1, 3, 7, 9
Numbers ending in other digits (0, 2, 4, 5, 6, 8) are necessarily divisible by either 2 or 5, and thus cannot be prime.
Also asked as:
- In a base-10 system, what four digits are the only possible endings for prime numbers greater than 5?