A hexagonal number is a figurate number that represents a hexagon. It 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. These numbers can be visualized as dots arranged in a hexagonal pattern. Hexagonal numbers are part of a broader category known as polygonal numbers, which also includes triangular and square numbers. They have applications in various fields, including mathematics and combinatorics, and are studied for their interesting properties and relationships with other types of numbers.