Are all square numbers even?

No, not all square numbers are even. Square numbers can be either even or odd, depending on the number that is squared. For example, the square of an even number is always even (like 2 x 2 = 4), but the square of an odd number is always odd (like 3 x 3 = 9). So, while square numbers like 4, 16, and 36 are even, others like 1, 9, and 25 are odd.