The number 3 is a natural number that comes between 2 and 4. It has many interesting mathematical properties:

• It is the 2nd prime number and the first super-prime number.
• 3 is the 4th Fibonacci number.
• It is the first Mersenne prime (3 = 2^2 - 1).
• It is the 2nd triangular number.
• It is the 2nd Sophie Germain prime.
• The cube of 3 is 27 (3^3 = 27).
• It is also related to several approximations in mathematics, such as approximations of π (pi), e, and √10.
• In the SI unit system, 10^3 = 1000 is called kilo (k), and 10^-3 is milli (m), both connected to powers of 3.

In summary, 3 is a small but very important and special number in mathematics with numerous unique characteristics and appearances in different contexts.