$ \begin{array}{r|l} 40 & 2\\ 20 & 2\\ 10 & 2\\ 5 & 5\\ 1 & \end{array} $
$40 = 2^3 * 5$
$2^2 = 4$;
$2^3 = 8$;
2 * 5 = 10;
$2^2 * 5 = 4 * 5 = 20$.
Ответ: 1, 2, 4, 5, 8, 10, 20, 40.