Solution: suppose the first four digits are x, then from the meaning of the question:

These eight digits xxxx(x- 1)(x-2)(x-3)(x-4).

And 4x+(x-1)+(x-2)+(x-3)+(x-4) =10 (x-3)+(x-4).

So x=8.

The telephone number of the teacher's home is 88887654.

^^~~~~~