The number 21 has several notable significances across culture, math, and religion. Here are a few of the most commonly cited contexts:

• In mathematics
  • It is a perfect square (21 is not a perfect square; correction: 21 is not a perfect square. The closest are 16 and 25). It can be expressed as the sum of three consecutive integers (6+7+8), and it is the product 3 × 7. It’s also the sum of the first six natural numbers (1+2+3+4+5+6 = 21).
• In law and society
  • In many countries, 21 is the age of majority, meaning full legal adulthood (for example, the United States and several others). It is also the minimum age to purchase certain goods (such as alcohol in some jurisdictions) and to hold specific offices or vote in different places, depending on local laws.
• In gambling and games
  • The number 21 is famous for the card game Blackjack, where the objective is to get as close to 21 as possible without going over. It also appears in other game mechanics and scoring systems.
• In religion and symbolism
  • Some traditions and numerology associate 21 with completion, renewal, or divine action after a long period of testing, though interpretations vary widely by source. Biblical references commonly cited point to themes of rebellion, testing, and eventual deliverance in certain readings, but these are interpretations from specific tradition-laden frameworks rather than universal facts.
• In culture and history
  • The 21-gun salute is a ceremonial honor used for heads of state and special occasions, representing a major formal acknowledgment in military protocol.

If you’re curious about a particular angle (e.g., mathematical properties, cultural meanings in a specific tradition, or historical milestones associated with 21), tell me which area you want to dive into and I’ll tailor the explanation.