The largest number with no repeated digits is 9,876,543,210 although it is 10 digits long, the largest 3 digit number with no repeated digits is 987
The largest ten digit number with no repeated digits is '9876543210'.
1023456789
987654
The greatest 4-digit number with no repeated digits is... 9876
The largest ten digit number with no repeated digits is '9876543210'.
The largest number with no repeated digits is 9,876,543,210 although it is 10 digits long, the largest 3 digit number with no repeated digits is 987
The largest ten digit number with no repeated digits is '9876543210'.
1023456789
987654
The greatest 4-digit number with no repeated digits is... 9876
10234567
98,764
94205 if digits are not to be repeated and 99999 if digits can be repeated
104 = 10000 if digits can be repeated, 5040 if not. The above answers assume a code can start with a 0. If not, 9000 if digits can be repeated and 4536 if not.
192 ways
1038, for example.