0
-39, itself, is the nearest integer.
The nearest integer to 13.5 is 14.
It is already rounded to the nearest integer.
It is not an integer, nor can it ever be an integer.
It can, however, be rounded to the nearest integer, in which case 0.1 will round to 0 to the nearest integer.
2,138.5 rounded to the nearest integer is 2,139