Simply rearranging the digits, the largest number is 5432. Much larger numbers are possible if other operations are allowed.
There are 4 possible numbers if the digits are not repeated; 18 if they are. Those are 3-digit numbers, assuming that zero would not be a leading digit. If zero is allowed for a leading digit, then you can have 6 for the non repeated, and 27 if repetition.
This permutation problem depends on whether the numbers are allowed to be repeated. If they are, there are a possible 9999 numbers, starting with 0001 and running sequentially to 9999. If they are not allowed to be repeated, there are a possible 5040 combinations.
Assuming no repeated digits, lowest first, 20; in any order 120; Allowing repeated digits: 216
1 set
Well, honey, the largest 12-digit number with repeated digits allowed is 9,999,999,999,999. I mean, unless you want to get fancy and start throwing in letters or emojis, but I doubt that's what you're looking for. So there you have it, the biggest 12-digit number you can get with the same digit repeated over and over again.
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'.
987654
The largest 10-digit number with no digit repeated is 9876543210 !
The largest ten digit number with no repeated digits is '9876543210'.
Repeated twice means we're allowed three of them. That would be 88,866,644. If you really meant repeated, that would be 88,664,420
97531
987654
9,999,999,999
987654