1 (Number)

1 (also called koow or kow in Somali) is the number that comes after zero and before two. It is the first of the natural numbers, used to denote a single unit or one thing only. The standard symbol is "1", derived from the Hindu-Arabic numerals; in Roman notation it is written as "I".

In mathematics, 1 has a special role: it is the multiplicative identity. This means that any number multiplied by 1 remains unchanged: n × 1 = n. Similarly, any number divided by itself equals 1 (provided it is not zero).

Mathematical properties

1 is the only natural number with exactly one divisor. For this reason, it is not counted among the prime numbers and is also not a composite number. The definition of a prime number requires two distinct divisors, 1 and itself; 1 does not meet this condition. When a number is factorized, 1 is not written because it does not change the result.

Any power of 1 is always 1: 1 to any power (1^n) equals 1. Similarly, any nonzero number raised to the power of zero equals 1 (n^0 = 1). The factorial of 1 is 1, and the factorial of zero is also 1. 1 appears at the beginning of the Fibonacci sequence (1, 1, 2, 3, 5...) when starting from one.

Use in measurement and convention

In measurement systems, 1 serves as the base unit: one meter, one kilogram, one second. In binary number systems, only 0 and 1 are used, which is the foundation of modern computers, where 1 represents the state "on" or "true". In percentages and proportions, 1 corresponds to 100%.

History of the symbol

The earliest counting systems used straight marks or lines to represent one thing, such as the Roman numeral "I" and ancient Egyptian and Mesopotamian notations. The symbol "1" used today comes from the Hindu number system, which was transmitted by the Arabs and reached Europe in the Middle Ages.