There are more than 20 chess pieces, first divide these chess pieces into several piles at random, and then perform the following operations: take out a chess piece from each pile at a time, form them into a new pile, and then arrange the piles from small to large , this process is a complete operation. After several times of operation, it is found that the number of piles of chess pieces and the number of chess pieces in each pile will not change. At this time, there are at least how many piles of chess pieces.
有20多颗棋子，先把这些棋子随意分成若干堆，然后进行下列操作：每一次从每一堆中取出一颗棋子，把它们组成新的一堆，后把各堆按照从小到大排列好，这一过程是一次完整的操作，当操作了若干次后，发现再继续这样操作过程，棋子的堆数以及各堆的棋子颗数都不会变了，此时至少有多少堆棋子．
<result>6</result>