How many groups of 6-digit numbers can you combine with 0-9? What are these numbers?

How many groups of 6-digit numbers can you combine with 0-9? What are these numbers?

It can be repeated that 9 * 10 * 10 * 10 * 10 * 10 = 900000
If it can't be repeated, 9 * 9 * 8 * 7 * 6 * 5 = 136080