Try this problem from I.S.I. B.Stat Entrance Objective Problem based on Sum of divisors and Integers.
The sum of all positive divisors of 1800, where 1 and 1800 are also considered as divisors of 1800, is
Integers
Sum of divisors
Exponents
Answer: 6045
B.Stat Objective Problem 99
Challenges and Thrills of Pre-College Mathematics by University Press
here 1800=(2)(2)(2)(3)(3)(5)(5) where n=\((p_1^a)(p_2^b)(p_3^c)\)
sum of divisors of 1800
=\((\frac{2^{4}-1}{2-1})\)\((\frac{3^{3}-1}{3-1})\)\((\frac{5^{3}-1}{5-1})\) where sum of divisors of n=\((\frac{p_1^{a+1}-1}{p_1-1})(\frac{p_2^{b+1}-1}{p_2-1})(\frac{p_3^{c+1}-1}{p_3-1})\)
=6045.
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