Hexagonal numbers are a type of figurate number that represent a hexagon. They can be calculated using the formula n(2n - 1) , where n is a positive integer. The first few hexagonal numbers are 1, 6, 15, 28, and 45. Each number corresponds to a hexagon that can be formed by arranging dots in a specific pattern. These numbers are closely related to other figurate numbers, such as triangular numbers and pentagonal numbers. Hexagonal numbers can also be visualized in a geometric arrangement, where each layer of dots forms a larger hexagon around the previous one. They have applications in various areas of mathematics and number theory.