Question

I am a number having three digits all of which are same. If you double
me, I will still be represented by three digits. That's true of other
numbers as well, but I am the largest than any of them. What am I?​

Answer 1

1000/2=500 the largest number.

However 500-1=499 the largest number when doubled is still a 3 digit number.

Proof:

2*499=998