Is 20 a perfect square? Yes, because there is a number, 40, that equals 20 . 2. Yes, because perfect squares must be even numbers and 20 is an even number.. Yes, beause 4 . 5=20 and 4 is a perfect square, so 20 is also a perfect square. No, because the only proper factors of 20 are 2, 4, 5, and 10, and none of these factors gives 20 when multiplied by itself.