Let four numbers from high to low be A, B, C and D respectively, where A, B, C and D are numbers from 0 to 9, and A is not 0.

Then1000a+100b+10c+d+a+b+c+d =1001a+1b+.

As 100 1A

10 1b+ 1 1c+2d = 1000

Since the maximum value of 1 1c+2d is11* 9+2 * 9 =117, it is the minimum value of1b.

So b can only be 9.

The above formula is simplified to 1 1c+2d=9 1. Obviously, the maximum c can only be 8.

Since 2d is even, the ratio of 1 1c is odd, that is, the ratio of c is odd, so the maximum value of c is 7.

Since the maximum value of 2d is 18, the minimum value of 1 1c must be 73, so the minimum value of c must be 7.

So c can only be 7.

d=7

The four digits are 1977.