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You're right, if we were talking prime numbers, sqrt(n) would make sense, but not for divisors.

[Edit]: Let me correct myself, if you add i and n / i at the same step, you're adding the other number that is also a divisor in same step, take for example 8, if i is 2, you'll end up adding sum += 2 + 8/2 which traduces to sum += 2 + 4, both 2 & 4 are divisors of 8, keep doing that and you'll soon notice that this way the i variable only needs to go up to sqrt(n).

## Day 19: Interfaces

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how is this correct for a number like 20? 10 is larger than sqrt(20), am confused here

You're right, if we were talking prime numbers,

`sqrt(n)`

would make sense, but not for divisors.[Edit]:Let me correct myself, if you add`i`

and`n / i`

at the same step, you're adding the other number that is also a divisor in same step, take for example`8`

, if`i`

is`2`

, you'll end up adding`sum += 2 + 8/2`

which traduces to`sum += 2 + 4`

, both`2`

&`4`

are divisors of`8`

, keep doing that and you'll soon notice that this way the`i`

variable only needs to go up to`sqrt(n)`

.yes i got it thank you very much

If n=1, then this would return 2, no? even though it should return 1.