Question: how many combinations can you make with 9 numbers?
Answer: There are 512 (2 to the 9th power) different permutations for any two numbers to be used in a 9 digit number. 45 x 512 = 23,040 - 10 = 23,030. This is the total number of unique combinations for 2 different numerals to appear as a 9 digit number.