+243 The number $100$ has four perfect square divisors, namely $1,$ $4,$ $25,$ and $100.$
What is the smallest positive integer that has exactly $2$ perfect square divisors?
+1233
The number $100$ has four perfect square divisors, namely $1,$ $4,$ $25,$ and $100.$
What is the smallest positive integer that has exactly $2$ perfect square divisors?
That would be 4. Its two perfect square divisors are 1 and 4.
We ignore 2 as a divisor of 4 because it isn't a perfect square,
just as the example given in the problem ignored 10 and 20, etc.
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