4649

This number is a prime.

+ The smallest composite-digit prime whose prime factors of its digits form another prime when they are concatenated left-to-right. [Honaker]

+ The greatest prime factor of any seven-digit repdigit. [La Haye]

+ 4649 is formed from two consecutive semiprimes (46 and 49); each of them formed from semiprime digits. [Silva]

+ The smallest prime whose each digit as well as number of digits are all composite numbers. [Gudipati]

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

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