Prime Numbers
Prime numbers by definition, are natural numbers that are evenly divisible by only 1 and itself, having two distinct factors.  The first prime number, therefore, is 2, and not 1.

Prime numbers are truly unique and one of the most interesting components in the entire field of mathematics.  They spark interest from the student learning arithmetic to the professors teaching at Yale University.  Why are they so interesting?

Although the average student won’t go in-depth very much into the study or usage of prime numbers, they are still useful to not only memorize, but to know various applications of them.