8642 is the greatist number if all the numbers are not the same and even
98
The greatest 3 digit number is 999, and all three digits are the same.
88888888
It is composite, as are all whole numbers whose last digits are even.
The greatest possible number is 888... (repeating).
All numbers are made with digits and there is no limit on how big they can be. So there is no greatest number.
8642 is the greatist number if all the numbers are not the same and even
If the digits go from the thousands place to the ones place then we need to use 4 digits. Because the digits are all even, we are forced to use the 4 even digits (2, 4, 6 and 8). As they decrease by 2 each time, the only option for ordering them is greatest to lowest. Therefore, the number described in the question is 8,642.
642
98
The greatest 3 digit number is 999, and all three digits are the same.
222
The number has to be 450. The number is 3 digits, and it's divisible by 8.
987,654,321
88888888
Most probably not. Almost all countries use an even number of character as the bank identifier. This is followed by an even number of digits representing the bank sort code and then another even number of digits representing the account number. Overall, this gives an even number of characters.