6. The sum of all four-digit numbers formed by four different non-zero digits without repetition is 106656, then the largest of these four-digit numbers is $\qquad$ , and the smallest is $\qquad$ .
【Answer】 9421,1249
【Analysis】
Let the smallest four-digit number be $\overline{a b c d}$, a total of $4 \times 3 \times 2 \times 1=24$ different four-digit numbers can be formed. Since each digit appears 6 times in each position, the sum of the 24 numbers is $6 \times(a+b+c+d) \times 1111=106656$, then the sum of the four digits is 16, so the maximum and minimum possibilities are 9421 and 1249, 8521 and 1258, 8431 and 1348, 7621 and 1267, 7531 and 1357, 7432 and 2347, 6541 and 1456, 6532 and 2356.