Fifty-one is the natural number that follows fifty and precedes fifty-two. It is an odd number and can be expressed as the sum of two prime numbers: 2 and 49. In Roman numerals, fifty-one is written as LI. In mathematics, fifty-one is significant as it is the product of three and seventeen, making it a composite number. Additionally, in the context of the United States, Area 51 is a highly classified military installation often associated with UFOs and extraterrestrial research, which has contributed to the number's cultural significance.