Mr. Li wrote several consecutive natural numbers starting from 1, 1, 2, 3, ... on the blackboard, and then erased one of them, and the average of the remaining numbers was 10.9, so what is the erased natural number?
李老师在黑板上写上若干个从1开始的连续自然数1，2，3，…，后来擦掉其中的一个，剩下的数的平均数是10.9，则擦掉的这个自然数是多少．
<gadget id="calculator">22 * 10</gadget>
<output>220</output>

<gadget id="calculator">220 + 11</gadget>
<output>231</output>

<gadget id="calculator">20 * 10.9</gadget>
<output>218</output>

<gadget id="calculator">231 - 218</gadget>
<output>13</output>

<result>13</result>