Multiply the natural numbers 1, 2, 3... together, if it is known that the last 13 digits of the product are exactly zero, then what is the smallest natural number that appears at the end?
把自然数1，2，3…乘到一起，如果已知这个乘积的最末13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>