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smc

number theory senior

Problem

For some positive integer , the number has positive integer divisors, including and the number . How many positive integer divisors does the number have?
(A)
(B)
(C)
(D)
Solution
Since the prime factorization of is , we have that the number is equal to . This has factors when . This needs a multiple of 11 factors, which we can achieve by setting , so we have has factors. To achieve the desired factors, we need the number of factors to also be divisible by , so we can set , so has factors. Therefore, . In order to find the number of factors of , we raise this to the fourth power and multiply it by , and find the factors of that number. We have , and this has factors.
Final answer
D