The factors of 18 are :- 18, 9, 6, 3, 2, 1
The largest factor other than 18 is therefore 9.
The digit 9 is the largest you can write in any place, including the tens place.
infinity
No.
There is no largest number. You can just keep going.
5678 + 8765 = 14443 would yield the largest possible sum.
99
Nine
9
The largest single digit in our numerical system is 9. Once you write 10, you have two digits.
9999 9999
99,999,998
The largest number you can write using Roman numerals without an overline at any symbol is 3999 (MMMCMXCIX), and the largest possible number is 3999999 (MMMCMXCIXCMXCIX, with an overline over the first nine letters.