In mathematics, negative two or minus two is an integer two units from the origin, denoted as −2 or −2. It is the additive inverse of 2, following −3 and preceding −1, and is the largest negative even integer. Except in rare cases exploring integral ring prime elements, negative two is generally not considered a prime number.
Negative two is sometimes used to denote the square reciprocal in the notation of SI base units, such as m·s−2. Additionally, in fields like software design, −1 is often used as an invalid return value for functions, and similarly, negative two may indicate other invalid conditions beyond negative one. For example, in the On-Line Encyclopedia of Integer Sequences, negative one denotes non-existence, while negative two indicates an infinite solution.