protected function _divisors()
    {
        if (!$this->_decimal()->zero) {
            throw new \RuntimeException('You can only get divisors from integers!');
        }

        $n = abs($this->value);
        $a = new A();

        for ($i = 1; $i <= $n; $i++) {
            if ($n % $i == 0) {
                $a->add(new self($i));
            }
        }

        return $a;
    }