In order to make the number as big as possible, you would want the greatest value digits in the greatest place value. Thus the first number would have to be 9. Once 9 has been used, the second number would have to be 8. Then the third number would have to be 7 and so on. Therefore, the greatest 9 digit number with 9 different digits is 987,654,321.
9,999,876 is the greatest seven-digit number using four different digits.
greatest number9999987
987654
98
3201
9,999,876 is the greatest seven-digit number using four different digits.
greatest number9999987
9,876,543 is.
98
987654
3201
That would be 99987.
9876 and 1234
999987
99,999,876
99,999,987
The greatest 4-digit number with no repeated digits is... 9876