Fill in the blanks: I. Sum of integer and its additive inverse is . II. Sum of -32 and -26 is . III. -36 / = -9. IV. Integers are closed under addition, multiplication and .

Here are the completed blanks:

I. Sum of integer and its additive inverse is $\boxed{\text{0}}$.
An additive inverse of an integer $x$ is $-x$. Their sum is $x + (-x) = 0$.

II. Sum of $-32$ and $-26$ is $\boxed{\text{-58}}$.

$$-32 + (-26) = -32 - 26 = -58$$

III. $-36 \div (\boxed{\text{4}}) = -9$.
To find the missing number, divide $-36$ by $-9$:

$$\frac{-36}{-9} = 4$$

IV. Integers are closed under addition, multiplication and $\boxed{\text{subtraction}}$.
Integers are closed under these three operations because performing them on any two integers always results in another integer.