A square number is a number that is the result of multiplying an integer by itself. For example, 1, 4, 9, 16, and 25 are square numbers because they are the result of 1x1, 2x2, 3x3, 4x4, and 5x5 respectively. While square numbers can be odd or even, they are always whole numbers.
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The square of an even number is always even.
Assuming you know that your number is a perfect square, the square root of an even number is even, and the square root of an odd number is odd.
Write the prime factors as powers. In a square number, each prime number appears an even number of times - i.e., an even power. Examples: 4 = 22 (even power, this is a square) 144 = 24 x 32 (all powers are even, this is a square) 12 = 22 x 3 or 22 x 31 (3 has an odd power so it is not a square) (If a number is a perfect square, that is equivalent to saying that its square root is a whole number.) * * * * * In this case there is a particularly fast method. The number ends in 0 so 10 must be a factor of the number. That is to say, 2 and 5 must be prime factors of the number. If it is a square then 22 and 52 must be factors of the number ie 22 x 52 = 100 must be a factor. But if 100 is a factor, the number must end in 00. It does not so it cannot be a square.
64
16, 36, 64, 100, 144, 196 etc The square of any even number is a multiple of 4 because an even number is 2n and (2n) squared is 4 (n squared).