3 is the second prime number, and the second single digit prime number. 3's prime factors are 1 and 3. It is said to be the first odd prime, because the previous prime number is 2, which is even.

It is also the first Fermat number.

## Proofs

- It is divisible by 1: 3/1=3
- It is
**not**divisible by : 3/2=1.5 - It is divisible by : 3/3=1
- Therefore it has 2 factors, not 3, because 3 divided by 2 does not result in an integer value.

## Relationship with other odd numbers

### The numbers before

- 2 is the first prime number. It is the only
**even**prime number. **1**, the number before 2, is**not**a prime number.

### The numbers after

- The next odd number, 5, is a prime number.
- There are no odd numbers between 3 and 5. As a result, they are twin primes.

- 7, the odd number following 5, is a prime number.
- 3 and 7 are four numbers apart, therefore, they are cousin primes.

- 9, the odd number following 7, is not a prime number. It is a square number, and the first odd composite number.

## Usage

### General

- Trilogy refers to a set of three works of art that are connected, either as a single work or three individual works.

### Science

- Lithium's atomic number and number of electrons are 3.
- Group three elements also have the valence of +3. Similarly, group five elements have the valence of -3.
- Tritium / hydrogen-3, has a nucleon number of 3.

### Sports

- In basketball, a shot behind the three-point arc is worth three points, unless in the 3x3 variant.
- In baseball, 3 strikes are required for the player to be considered "out", and 3 outs are required for the attacking team to exchange with the opposing team.

### Video Games

- In The Legend of Zelda series, there is a sacred relic called Triforce, which consists of three separate golden triangles.