173□ is a four-digit number. The math teacher said: "I filled in 3 numbers in the box, and got 3 four-digit numbers, which are divisible by 9, 11, and 8 in turn." What is the sum of the numbers?
173□是一个四位数．数学老师说："我在其中的方框内先后填入3个数字，得到3个四位数，依次能被9、11、8整除，"问：数学老师在方框中先后填入的3个数字之和是多少？
<gadget id="calculator">7 + 8 + 6</gadget>
<output>21</output>

<result>21</result>