16407.
An integer is a whole number that doesn't need to be written using a fraction or decimals. (Some examples of integers are 4, 50, and -3; on the other hand, fractions or decimals like 1/2 or .3 are not).
Because we round up a number when the decimal is greater than or equal to .5 (which in this case it is), we round 16406.5 to the next biggest integer, 16407.