20 young pioneers participate in voluntary labor, and are divided into several groups with equal numbers (the number of groups and the number of each group are not less than 2), how many ways can there be at most?
20名少先队员参加义务劳动，分成人数相等的若干小组(组数和每组人数都不少于2)，最多有多少种分法．
<result>4</result>