3 (number)

3 (Somali: saddex, also written sadax or sadex) is a natural number that follows 2 and precedes 4. It is an odd number and the smallest prime number greater than 2; only 1 and 3 divide it without remainder.

The symbol '3' in the Hindu-Arabic numeral system underwent various historical transformations originating from Indian scripts, later transmitted to the Middle East and Europe. Other numeral systems, such as Roman numerals, represent it as III.

Mathematical properties

3 is the second prime number after 2. It is also the third number in the Fibonacci sequence (1, 1, 2, 3, 5). If the sum of a number's digits is divisible by 3, then that number is divisible by 3—this is known as the divisibility rule of three. Since 1 + 2 = 3, the number 3 is a triangular number rather than a perfect number.

Geometry

Three non-collinear points define a single plane. The triangle is the simplest polygon in planar geometry, with the sum of its interior angles equal to 180 degrees. Ordinary space is defined by three dimensions: length, width, and height.

Language and culture

In Somali, 'saddex' is a cardinal number, from which derive 'saddexaad' (an ordinal number) and 'saddexley' or 'saddex-geesle' (used in geometry). In many world cultures, three appears structurally in narratives and customs, such as the rule of three in oral storytelling.