rounding off to thousandths is referring to the hundredth number(3rd number from right)
if it's >5, it +1 to the thousand's number (4th number from right),
eg. 4570 rounded off by thousand = 5000
if <5 then it reduces to 0.
eg. 3489 rounded off by thousand = 3000
for your case, 2,181,465 rounded off to thousand = 2,181,000
