2, 2 even is impossible? there are those cases?

2, 3 even implies that the sequence of binary numbers is 11 between 2 and 3?

in a sequence of binary digits as 000, there is not an even number of 1's or an odd number of 1's. But it was always supposed to be even or odd ... But zero is not even or odd

???

Number 0 is even .. ;)