The number "421" is a three-digit integer that follows 420 and precedes 422. It is an odd number and can be expressed as the sum of the first 20 prime numbers, which are important in number theory and mathematics. In various contexts, "421" can also refer to specific codes or designations. For example, in the realm of aviation, it may represent a flight number, while in the context of law enforcement, it could denote a specific incident or report type. Understanding the context is essential for interpreting its meaning accurately.