SOLUTION: Find the largest four-digit number having exactly three factors, including 1 and itself

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Question 902001: Find the largest four-digit number having exactly three factors, including 1 and itself
Answer by MathLover1(20849) About Me  (Show Source):
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If 1 and itself are factors, then that leaves only one factor remaining to be found.
If there is only one factor, it must be a square root. The largest perfect square with four digits is 9801, but its square root is not a prime number; so there more than one additional factors.
The largest prime number less than 99 is 97 and 97%5E2=9409.

9409 has factors 1, 97, and 9409, and is the largest 4-digit number with three factors.