As mentioned, this is a trial-and-error process. I typed in the Avogadro's number 6.022×10²³ then added the largest number I could think of. Since infinity can be thought of as 99999...(and so on), I thought that the number should all be composed of 9. As I add 9 after one another, I ended with about 10 quadrillion before the display changed to 6.022000001×10²³. Therefore, the largest number is: 9,999,999,999,999,999.
