Let's

Let n n be a positive integer such that there exists positive integers x x and y y satisfying { lcm ( x , y ) = n ! gcd ( x , y ) = 1998 \begin{cases} \text{lcm}(x,y) =n! \\ \gcd(x,y) = 1998 \end{cases}

Which of the following options is true?

Notations:

  • lcm ( ) \text{lcm}(\cdot) denotes the lowest common multiple function.

  • gcd ( ) \gcd(\cdot) denotes the greatest common divisor function.

  • ! ! is the factorial notation. For example, 8 ! = 1 × 2 × 3 × × 8 8! = 1\times2\times3\times\cdots\times8 .

n > 36 n>36 n < 36 n<36 n > 37 n>37 n < 37 n<37

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1 solution

Let x=1998a, y=1998b. So a,b are positive integers such that a<b,gcd(a,b)=1. We have LCM(x,y)=1998ab=2×3^3×37ab=n!. Thus n>37.

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