29 and 31.
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Each of the 25 prime numbers from 1 to 100 has exactly two factors, 1 and the number itself. The other 75 numbers from 1 to 100 are not prime numbers because none of them have exactly two factors.
5 is prime, the rest aren't.
25 = 23 + 2
They are: 29 and 31
4 and 25 are not prime numbers.