Perfect numbers P34091

Write a function that tells if a natural @n@ is perfect.

A natural number is called perfect if it is equal to the sum of all its divisors except itself. For instance, 28 is perfect, because $28=1+2+4+7+14$.

Interface

bool is_perfect(int n);

int is_perfect(int n);

public static boolean isPerfect(int n);

is_perfect(n)  # returns bool

is_perfect(n: int) -> bool

Precondition

@n@ is a natural number.

Observation

You only need to submit the required procedure; your main program will be ignored.