There are 604,661,760 combinations possible.
For the first character, there are 26+10 possible characters (26 letters plus 10 numbers). There are the same number of possible characters for the 2nd, 3rd, 4th and 5th character. For the last character, however, there are only 10 possible characters (numbers) to choose from. This gives us:
36(36)(36)(36)(36)(10) = 604,661,760
