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2017 AMC 10B Problem 20

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2017 AMC 10B Problem 20AMC 10 Step by Step
Name:                             Date: September 13, 2026
Divisibility & Factors · difficulty 3 of 5 · about 4 min · position P16-20

The number 21!=51,090,942,171,709,440,00021!=51,090,942,171,709,440,000 has over 60,00060,000 positive integer divisors. One of them is chosen at random. What is the probability that it is odd?

  1. A)

    121\frac{1}{21}

  2. B)

    119\frac{1}{19}

  3. C)

    118\frac{1}{18}

  4. D)

    12\frac{1}{2}

  5. E)

    1121\frac{11}{21}

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