Question: why zero is an even number?
Answer: In the group of zero objects, there is no leftover object, so 0 is even. There is another concrete definition of evenness: if the objects in a set can be placed into two groups of equal size, then the number of objects is even. ... For example, 1 is odd because 1 = (2 × 0) + 1, and 0 is even because 0 = (2 × 0) + 0.