221 (number)

In mathematics

• a product of two prime numbers, 13 and 17, making it a semiprime
• the sum of five consecutive prime numbers
• the sum of nine consecutive prime numbers
• a centered square number
• Mertens function = 5 a record high that stands until 554
• If you deal 2 cards from a single deck of 52 cards, you have a 1 in 221 chance of getting 2 aces.

  In other fields

• SMTP status code for service closing transmission channel
• 221B Baker Street, the fictional London residence of Sherlock Holmes
• The experiment number for Sparky in the Disney franchise Lilo & Stitch.
• .221 Remington Fireball, firearm cartridge

  Historical years

• 221 A.D. and 221 B.C.