69

This number is a composite.

10⁶⁹ + 69 is prime. [Gupta]

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]