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AMO 2018 Secondary 2 (Grade 8) Question 21

AMO · AMO 2018 Secondary 2 (Grade 8)

Question 21

How many nonnegative integers $M$ satisfy exactly three of these statements? (1) $M$ is prime. (2) $M+3$ is prime. (3) $1<\sqrt M<8$. (4) $M+5$ has an odd number of positive divisors.

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