207, 2007, 20007, ... among the numbers whose first digit is 2, units digit is 7, and the middle digits are all 0, what is the smallest number that can be divisible by 27 but not divisible by 81?
207，2007，20007，…等首位是2，个位是7，中间数字全部是0的数中，能被27整除而不被81整除的最小数是多少．
<result>20_000_007</result>