This number is a prime.
Single Curio View: (Seek other curios for this number)521 is the sum of two squares (112 + 202). Note that 11 + 20 is a Mersenne prime exponent as well. [Luhn]
Submitted: 2002-01-04 13:16:27; Last Modified: 2008-01-30 11:28:00.
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