defmodule PerfectNumbers do
  @doc """
  Determine the aliquot sum of the given `number`, by summing all the factors
  of `number`, aside from `number` itself.

  Based on this sum, classify the number as:

  :perfect if the aliquot sum is equal to `number`
  :abundant if the aliquot sum is greater than `number`
  :deficient if the aliquot sum is less than `number`
  """
  @spec classify(number :: integer) :: {:ok, atom} | {:error, String.t()}
  def classify(number) do
  end
end