The number 1 (one) is the first and smallest positive integer in the natural number sequence. It represents a single unit or entity and serves as the fundamental unit of counting and measurement. In mathematics, 1 is known as the multiplicative identity because any number multiplied by 1 remains unchanged. It is neither considered a prime nor a composite number by modern convention. The number 1 is unique in that it is its own factorial, square, cube, and any other power, all equal to 1. It also represents the "on" state in binary code, which is foundational to digital technology and computing. Historically, the glyph for 1 evolved from ancient Sumerian and Babylonian symbols through Indian scripts to the modern Arabic numeral. It is often depicted as a vertical line with a serif at the top, sometimes with a horizontal line at the bottom, which varies by region. Philosophically, 1 symbolizes unity, the ultimate reality, or the source of existence in various traditions. In computer science, 1 corresponds to the Boolean value "true," contrasting with 0 as "false." In summary, 1 is a fundamental number with unique mathematical properties and broad significance across science, technology, language, and philosophy