Hint 1:

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How do you know whether a number i is a factor of another number n.

Hint 2:

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What is the range in which the factors of any number n lie? What is the smallest factor of n and what is the largest factor of n?

Hint 3:

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Observe that factors always occur in pairs. e.g. Consider the factors of 36. If you know that 1 is a factor of 36, you also know that 36 is a factor of 36 (you didn’t need to check it again). Similarly, if you know that 2 is a factor of 36, then so is 18.

Hint 4:

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Extending the idea of factors occurring in pairs. We can say that if i is a factor of n, then so is n/i.

Hint 5:

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When do factors start repeating? Till when do you need to check that if i is a factor of n.

Try to enlist factors of various numbers like 12, 24, 36, 40. And try to figure out a point where the factors start repeating.

Hint 6:

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Spoiler Alert: This provides the answer to the above hint.

We can see that factors start repeating when i = n / i \Rightarrow i^2 = n \Rightarrow i = \sqrt(n).

Hint 7:

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Now, you know the range in which you need to check whether i is a factor of n or not. Just sum over all factors and check whether the sum is equal to the original number n or not.

Hint 8:

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Try to print the sum of factors. Check whether it is correct for square numbers or not. Are you adding something extra.

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