The number n=112011⋅201111 is given. How many divisors that are less than n and are not divisors of n, does n2 have?
Solution
The number of divisors of n2=114022⋅201122 is: N=(4022+1)(22+1)=92529. We can pair the divisors of n2 in a way d and dn2 where one divisor is greater than n, another one is less. The number n does have a pair, therefore the number of divisors that are less than n is 292529−1=46264.
The number N1 of divisors of n that are less than n is: N1=(2011+1)(11+1)−1=24143. So the number we are looking for is 46264−24143=22121.
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