Including the leading zero, then the answer is 210.
Or, allowing for repeating numbers, 10000.
There are 1,120,529,256 combinations.
If every number can be used as many times as you like, there are 104 = 10000 different combinations. If each number can only be used once, there are 9!/(9 - 4)! = 5040 combinations.
There are 9C3 = 84 combinations.
9
There are 45 combinations.
There are a huge number of combinations of 5 numbers when using the numbers 0 through 10. There are 10 to the 5th power combinations of these numbers.
9
9000
The number of combinations is 10C4 = 10*9*8*7/(4*3*2*1) = 210
24
There are only 10 combinations. In each combination one of the 10 digits is left out.
If the numbers can be repeated and the numbers are 0-9 then there are 1000 different combinations.