Without a decimal point, six can.
With a decimal point, eighteen can.
If the digits are all different then 18. Otherwise, 192.
If they can be repeated, 343 different numbers. If they can be used once each, there are only 210.
24 different numbers.
There are 60480 numbers.
20 of them, if repetition is not allowed.
99999
There are 4^6 = 4096 such numbers.
8.
125
89,999 different numbers i guess
1,000
10