We can choose the 1st digit any of 9 ways (can't choose 0). Then we can choose the 2nd digit any of the 9 remaining ways (can choose 0). Then we can choose the 3rd digit any of the 8 remaining ways. Then we can choose the 4th digit any of the 7 remaining ways. Then we can choose the 5th digit any of the 6 remaining ways. Then we can choose the 6th digit any of the 5 remainingways. Answer: 9*9*8*7*6*5 = 136080 ways. Edwin