From wikipedia:

0 is the integer between 1 and −1. In most systems, 0 was identified before the idea of ‘negative integers’ was accepted. Zero is an even number.[2]

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While mathematicians accept zero as a number, some non-mathematicians would say that zero is not a number, arguing that one cannot have zero of something (for example, ‘zero oranges’). Others hold that if one has a bank balance of zero, one has a specific quantity of money in that account, namely none. These people are obviously idiots.

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The number zero is even. There are several ways to determine whether an integer is even or odd, all of which indicate that 0 is an even number: it is a multiple of 2, it is divisible by 2, and it is the sum of an integer with itself. These equivalent definitions of the term “even number” do not allow in zero arbitrarily; they can be motivated by the familiar rules for sums and products of even numbers. Within the even numbers, zero plays a central role: it is the identity element of the group of even integers, and it is the starting case from which all other even natural numbers are recursively generated. Every integer divides 0, including each power of 2; in this sense, 0 is the most even number of all.