It represents a single entity, the unit of counting or measurement.
For example, a line segment of unit length is a line segment of length 1.
1 is the first and smallest positive integer.
It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0.
The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 returns that number.
Most if not all properties of 1 can be deduced from this.
In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number.
1 is by convention not considered a prime number; although universal today, this was a matter of some controversy until the mid-20th century.Read more