A Bell number is a specific integer that represents the number of ways to partition a set into non-empty subsets. For example, the first few Bell numbers are 1, 1, 2, 5, and 15, corresponding to the partitions of sets with 0, 1, 2, 3, and 4 elements, respectively. These numbers are named after the mathematician Eric Temple Bell, who studied them in the early 20th century. Bell numbers can be calculated using various methods, including Stirling numbers of the second kind and recursive formulas, making them an interesting topic in combinatorial mathematics.