The thousand's place cannot be zero as it has to be a three digit number. Therefore, there are nine ways of filling the thousands place (1,2,3,4,5,6,7,8,9). The hundreds place can be filled in 9 ways(except the digit placed in thousands place, every other digit can come including zero). The units place can be filled in 8 ways(except the two digits placed in the hundreds and thousands place).
Therefore, total number of ways=9*9*8=81*8=648 ways