How many positive integers are there for which is divisible by ?
Solutions — 2
Solution 1
If , then . As , there are 7 possibilities.
If , then . As , there are 3 possibilities.
If , then . As , there are 2 possibilities.
If , then . As , there is 1 possibility.
Those add up to 13 possibilities.
Solution 2
As the number is always a divisor of , the number is a divisor of if and only if is a divisor of . The canonical representation shows that the number of divisors of is . The middle one of them is 2014 and 13 divisors are expressible in a form for some positive integer . Thus there are 13 possibilities for .
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