Imaginary numbers aren't integers. An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit i, which is defined by its property i2 = −1. 5i is an imaginary number, and its square is −25. Zero is considered to be both real and imaginary.√2 is irrational. Just like rational numbers have repeating decimal expansions (or finite ones), the irrational numbers have no repeating pattern. Together, the irrational and rational numbers are called the real numbers which are often written as . These are all numbers we can see along the number line.