A three-digit number, all of which are not 0, the digits are scrambled, and the largest number is 594 greater than the smallest number. What is the largest sum of the digits of this three-digit number?
一个三位数，各位皆不为0，将数位打乱，排出的最大数比最小数大594，问这个三位数各数位之和最大是多少．
<gadget id="calculator">9 + 9 + 3</gadget>
<output>21</output>

<result>21</result>