The sum of three consecutive natural numbers is 21, what is the least common multiple of these three numbers?
三个连续自然数的和是21，这三个数的最小公倍数是多少．
<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">6 * 7 * 2 * 2</gadget>
<output>168</output>

<result>168</result>