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# 209

The curve 42*x*^{2} - *y*^{2} = 209 contains
the 'prime points' (3, 13), (5, 29), (7, 43), and (13, 83). [Buddenhagen]

209 = 11 x 19 is a member of a series *n*(*n* + 1) - 1 with the property that all terms greater than 1 are divisible by primes of form 10*k* + 1 or 10*k* - 1, but not 10*k* + 3 or 10*k* - 3. There is an infinity of pairs *x*,*y* where x^{2} - y^{2} - *x**y* = 209 for *x*, *y* integer. [McNamara]

The smallest composite primorial - 1.

The number of consecutive composite numbers that follow the prime 20831323, the first prime gap exceeding 200.

(There is one curio for this number that has not yet been approved by an editor.)

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