Which number is an irrational number?

The square root of 3 is irrational because 3 is not a perfect square, so its square root cannot be written as a ratio of integers. Its negative, negative square root of 3, is also irrational. The other choices are rational: 2.56 is a terminating decimal, the square root of 16 is 4, and negative 22/9 is a ratio of integers.

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