Let’s use the digits in this way:

To minimize the number, the smaller digits will be used in left side;

And, to maximize the number, larger digits are used in left side. [As the left side digits contributes more towards the value of the number: Any number, say, ”a_na_{n - 1}a_{n - 2….}a₁a₀ can be expanded as :

= a_n × 10ⁿ + a_{n - 1} × 10^{n - 1} + a_{n - 2} × 10^{n - 2} + a_{n - 3} × 10^{n - 3} + … + a₁ × 10¹ + a₀]

The greatest = 765420;

and the smallest = 204567

[Note, 0 can not be used in starting the number, so second smallest digit, available, 2 is used as starting digit].

Their sum

= 969, 987