9,876,543 is.
9,999,876 is the greatest seven-digit number using four different digits.
greatest number9999987
98
987654
3201
The greatest 4-digit number with no repeated digits is... 9876
That would be 99987.
99,999,876
99,999,987
999987
9876 and 1234
The greatest 3 digit number is 999, and all three digits are the same.