I think 9 or similar numbers like 99, 999 etc are most searched numbers or even 888 is also famous in poker and casino world
I make a check in google trends and the most popular is number 2 Second is number 3 and trird is numbers 1 and 4
How can you be so certain that everybody else is wrong and only 18 is the correct answer? Do you have any logic/theory supporting your claim? Regards, RightMan