69
This number is a composite.
sigma(69) = reversal(69). [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]
(There are 5 curios for this number that have not yet been approved by an editor.)
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