Four is the smallest composite number;

What is the Smallest Composite Number? A composite number has more than two factors, other than 1 and the number itself. Here, 4 satisfies this condition, and there is no other number smaller than 4 which is composite. Therefore, 4 is the smallest composite number.

It is also the smallest Smith number;

The smallest non-cyclic group has four elements;

Four is the maximal degree of the equation that can be solved in radicals;

There is a four-color theorem that states that any map can be colored in no more than four colors in such a way that no two adjacent regions are colored in the same color;

Lagrange's four-square theorem states that every positive integer can be written as the sum of at most four square numbers;

Four is the maximum number of dimensions of a real division algebra;

In bases 6 and 12, 4 is a 1-automorphic number;

And there is a lot more cool stuff about this number! Four is the smallest composite number;

It is also the smallest Smith number;

The smallest non-cyclic group has four elements;

Four is the maximal degree of the equation that can be solved in radicals;

There is a four-color theorem that states that any map can be colored in no more than four colors in such a way that no two adjacent regions are colored in the same color;

Lagrange's four-square theorem states that every positive integer can be written as the sum of at most four square numbers;

Four is the maximum number of dimensions of a real division algebra;

In bases 6 and 12, 4 is a 1-automorphic number;

And there is a lot more cool stuff about this number!