Multiply several natural numbers 1, 2, 3, ... together, if it is known that the last thirteen digits of the product happen to be zero, what is the smallest natural number that appears at the end?
把若干个自然数1，2，3，…乘到一起，如果已知这个乘积的最末十三位恰好都是零，那么最后出现的自然数最小应是多少？
<gadget id="calculator">50 + 5</gadget>
<output>55</output>

<result>55</result>