The number 3 is a natural number that comes after 2 and before 4. It is a prime number and has several interesting mathematical properties:

• It is the only natural number that is equal to the sum of the two preceding natural numbers (1 + 2 = 3).
• 3 is also equal to the sum of the factorials of the two preceding natural numbers (1! + 2! = 3).
• The square of 3 is 9.
• It is the smallest Mersenne prime number.
• The number 3 is a triangular number, being the sum of the first two natural numbers.
• Any number whose digits sum to a multiple of 3 is itself divisible by 3.
• In geometry, three lines meeting form a triangle, the simplest polygon with three vertices and three edges.
• In three-dimensional space, three points determine a plane.
• The number 3 is significant in various cultural and religious contexts, often symbolizing completeness or divine unity, such as the Christian Holy Trinity.

In numeral systems, 3 is represented as "III" in Roman numerals, "11" in binary, and "3" in octal, decimal, and hexadecimal systems. Additionally, 3 is used in various practical contexts:

• Tripods have three legs for stability.
• The atomic number of lithium is 3.
• In electronic color coding, the number 3 corresponds to the color orange.

These points summarize the mathematical, physical, and symbolic significance of the number 3