After rearranging the order of the four-digit numbers, some new four-digit numbers can be obtained. There is a four-digit number M, which is 7956 smaller than the largest new number and 396 larger than the smallest new number. Find the four-digit number and briefly explain why. (The four numbers of M can be the same, but the number 0 is not included).
将四位数的数字顺序重新排列后，可以得到一些新的四位数．现有一个四位数M，它比新数中最大的小7956，比新数中最小的大396．求这个四位数，并简述理由．(M的四个数码可以相同，但不含数码0)．
<gadget id="calculator">9_951 - 7_956</gadget>
<output>1_995</output>

<result>1_995</result>