when rounding a number to the nearest thousand we have to first check the digit in the hundreds place.
if the digit in the hundreds place is equal to or greater than 5 then we increase the value of the thousands place by 1
If the digit in the hundreds place is lesser than 5 then there's no change to the digit in the thousands place
number given is 18 366
digit in the thousands place is 8
digit in the hundreds place is 3. This is lesser than 5 therefore no change is done to the digit in the thousands place. So no change is done to 8.
therefore 18 366 rounded off to the nearest thousand is
18,000