221

221 = 13 x 17.

221 = 2*3*5*7 + 11 = 13*17. Note the consecutive use of the first seven primes.

221 has two representations as a sum of two squares: 221 = 5² + 14² = 10² + 11².

221 is the hypotenuse of two primitive Pythagorean triples: 221² = 21² + 220² = 140² + 171².

221 is a centered square number.

221b, Baker Street, London, England is the address of fictional detective Sherlock Holmes.

Source: Prime Curios!