Thursday, August 2, 2012

409

409 is a prime number.

409 is a centered triangular number.

409 has a representation as a sum of two squares: 409 = 32 + 202.

409 is the hypotenuse of a primitive Pythagorean triple: 4092 = 1202 + 3912.

409 is the smallest prime that, along with both its prime neighbors, uses non-prime digits: 401, 409, 419.

409 is the number of primes less than 10,000 that form members of twin prime pairs.


Source: Prime Curios!

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