2018 UNCO Math Contest II Problems/Problem 4

Problem

How many positive integer factors of $36,000,000$ are not perfect squares?

Solution

We can use complementary counting. Taking the prime factorization of $36,000,000$ , we get $2^8\cdot3^2\cdot5^6$ .So the total number of factors of $36,000,000$ is $(8+1)(2+1)(6+1) = 189$ factors.

Now we need to find the number of factors that are perfect squares. So back to the prime factorization, $2^8\cdot3^2\cdot5^6 = 4^4\cdot9^1\cdot5^3$ . Now we get $(4+1)(1+1)(3+1)=40$ factors that are perfect squares.

So there are $189-40=\boxed149$ positive integer factors that are not perfect squares.

~Ultraman

2018 UNCO Math Contest II (Problems • Answer Key • Resources)
Preceded by Problem 3	Followed by Problem 5
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2018 UNCO Math Contest II Problems/Problem 4

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