# 209

This number is a composite.

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.

209^0 + 209^1 + 209^2 is a prime number. [Raghava]

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

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