0 (zero)
There has been discussion for centuries about whether or not the digit 0 is a number. Nowadays we call it a number, and for writing decimal numbers we just need it.
Explanation
With addition and subtraction there are no problems
and
A multiplication works well
and
In a division only the numerator can be zero and the denominator may never be zero, so
Surprisingly, dividing by zero produces two results
and moreover, infinity has no specific value. However, zero divided by zero is
Exponentiation is possible, and so
but zero to the power of zero cannot be calculated, and is determined by definition as
The square root of zero is
Additional informatie
In 628, the Indian astronomer Brahmagupta was the first to give rules to compute with zero.