Tuesday, July 14, 2009

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!

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