$1008$
Since 1008 is the first 4-digit number we found that satisfies the condition, it is the least 4-digit number exactly divisible by 9. Both methods confirm that 1008 is the smallest 4-digit number that is exactly divisible by 9.
Which is greater: √45 or √49 - 1?
Replace the question mark (?) in the following number series with suitable option.
$3, 3, 4.5, 9, 22.5, ?$