def classify(number):
    """A perfect number equals the sum of its positive divisors.

    :param number: int a positive integer
    :return: str the classification of the input integer
    """
    if number <= 0:
        raise ValueError(
            "Classification is only possible for positive integers.")
    aliquot_sum: int = 0
    # find divisors and store them in a list
    for divisor in range(1, (number // 2) + 1):
        if not number % divisor:
            aliquot_sum += divisor
    if aliquot_sum == number:
        return "perfect"
    elif aliquot_sum > number:
        return "abundant"
    else:
        return "deficient"