What is the largest six-digit number with an odd number of positive factors?

Question

What is the largest six-digit number with an odd number of positive factors?

So I know the number must be a perfect square, but how do I know six-digit number perfect squares? I'm pretty sure there's a much easier way to solve/approach this problem.

The answer's supposed to be 998,001.

Answer 1

The first seven-digit square is $1000^2$. Thus the last six-digit square is $999^2=998001$.