98
If repeated digits are allowed, then the largest 12-digit number is 999,999,999,999 .If repeated digits are not allowed, then the largest 12-digit number is 989,898,989,898 .If the same digit can't be used more than once, then the largest possible number has only10 digits. The number is 9,876,543,210 .
9876
99,998,765
99,998,765
999,987,654
9998888
An eight digit number with one zero cannot remain the same when its digits are reversed. It must have an even number of 0s.
987654
948,765,321
A palindrome reads the same forward and in reverse. This tells me that at leastthe first digit and the last digit must be the same. So it's not possible to have a6-digit palindrome "with no same digits".The largest 6-digit palindrome, with just enough repetition of digits to make it apalindrome and no more, would be 987,789 .
3333
It is 987654321.