GMAT Problem Solving (PS) | Re: How many unique positive divisors does 441 have?

To determine the number of factors of a number, we add one to each exponent associated with each unique prime factor and that product will equal the number of factors of a particular number. Let’s apply this rule to 441.

441 = 7 x 63 = 7 x 7 x 9 = 7^2 x 3^2

Thus, 441 has (2 + 1)(2 + 1) = 3 x 3 = 9 total factors.

Answer: C

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