If three consecutive natural numbers are multiples of 17, 19, and 21, what is the smallest number among the three consecutive natural numbers?
如果三个连续自然数依次是17，19，21的倍数，那么这三个连续自然数中最小的那个数最小是多少．
<gadget id="calculator">17 * 19 * 21</gadget>
<output>6_783</output>

<gadget id="calculator">6_783 + 17</gadget>
<output>6_800</output>

<gadget id="calculator">6_800 / 2</gadget>
<output>3_400</output>

<result>3_400</result>