Lets say you have a number x. x could be 2 or 3 or whatever. If you are only told it is x then you don't know if it is odd or even.

So x could be odd or even

If you add 1 to x you get x + 1

Now x + 1 could also be odd or even but it is the opposite odd/even to x

If x is 2 (even) then x + 1 is 3 (odd) If x is 3 (odd) then x + 1 is 4 (even)

if x is infinite (all the numbers added up) then x + 1 is also infinite but infinity is not equal to infinity + 1 Because there are different infinities, we could keep adding 1 to that number forever producing different infinities

we don't know that inifinity is odd or even but we do know that infinity + 1 is the opposite odd/even to inifinity.

Therefore there are infinities that are odd and infinties that are even but we cannot determine wether a specific inifinity is odd or even.