For a four-digit number, the sum of its digits is 10 times smaller than the number itself by 1989, and the sum of its digits is 100 times smaller than the number itself by 909. What is the four-digit number.
一个四位数，它各位数字和的10倍比这个数本身小1989，它的各位数字和的100倍比这个数本身小909．求这个四位数为多少．
<gadget id="calculator">1_989 - 909</gadget>
<output>1_080</output>

<gadget id="calculator">1_080 / 90</gadget>
<output>12</output>

<gadget id="calculator">12 * 100</gadget>
<output>1_200</output>

<gadget id="calculator">1_200 + 909</gadget>
<output>2_109</output>

<result>2_109</result>