The numbers 1, 2, 4, 5, 8, 10, and 20 are all integers that can be classified as whole numbers. They are often used in basic arithmetic and can represent quantities, rankings, or measurements. For example, 1 is the smallest whole number, while 20 is the largest in this set. These numbers can also be found in various mathematical contexts, such as factors and multiples. For instance, 4 is a multiple of 2, and 10 is a multiple of 5. Additionally, 8 is a power of 2, specifically 2^3.