This number is a prime.

+ The Carillon Residences North Tower in Miami Beach is 397 feet tall.

+ Conjectured to be the largest prime that can be represented uniquely as the sum of three positive squares (3^2 + 8^2 + 18^2). [Noe]

+ The prime that splits into a prime pair (3, 97) with sum one hundred and minimal product (3*97=291). Note that the sum-product concatenation 100291 is prime, and that 397 is a left-truncatable prime, just like its counterpart prime 5347 that splits into two complementary primes (53, 47) also summing up to a hundred, but with maximum product (53*47=2491). The reversal of whose sum-product concatenation however being also prime (1942001). [Beedassy]

+ Iranian grandmaster Morteza Mahjoob won 397 (of his 500) chess games to break the Guinness Book World Record for the most number of simultaneous matches in August 2009.

+ 397 and 401 are the largest pair of consecutive primes that together have no duplicate digits. [Gaydos]

(There are 3 curios for this number that have not yet been approved by an editor.)

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