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!
