69

This number is a composite.

+ 1069 + 69 is prime. [Gupta]

+ sigma(69) = 96. [Honaker]

+ The sum of the first non-primes less than or equal to 69 is prime. [Patterson]

+ 100^69 - 69 is prime. Note that 69 is the smallest number with this property. [Firoozbakht]

+ The smallest strobogrammatic semiprime. [Capelle]

+ Strobogrammatic primes that don't use 6 or 9 are dihedral primes.

+ π(6) * prime(9) = 69. [Gupta]

+ The smallest multidigit strobogrammatic number n such that {n+2, n+4} and {n^3+2, n^3+4} are twin prime pairs. [Bajpai]

+ The square of 69 and cube of 69 combined together consist of all the digits (0-9). What a lucky number! [Obernhofer]

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