24:
1468
1486
1648
1684
1846
1864
4168
4186
4618
4681
4816
4861
6148
6184
6418
6481
6814
6841
8146
8164
8416
8461
8614
8641
99999
500
180 of them.
There are 5 numbers of 1 digit, 25 numbers of 2 digits, and 75 numbers of 3 digits. This makes 105 numbers in all.
There are 34 = 81 numbers.
99999
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
24
500
840
There are 60480 numbers.
180 of them.
There are 3024 of them.
1 set
There are 5 numbers of 1 digit, 25 numbers of 2 digits, and 75 numbers of 3 digits. This makes 105 numbers in all.
There are 4^6 = 4096 such numbers.
If the digits are all different then 18. Otherwise, 192.