168

This number is a composite.

+ The number of primes less than or equal to a thousand (π(1000) = 168) equals the number of hours in a week (7 * 24 = 168). [Honaker]

+ 168 = sigma(sigma(sigma(1+6+8))) and 1+6+8 = π(1*6*8). 168 is the only number with these two properties. [Firoozbakht]

+ All known prime powers p^n are pandigital for n > 168. [Gupta]

+ 168 is the product of the first two perfect numbers. [Laughlin]

+ The sum of all terms on the Ishango bone coincides with the number of primes less than a thousand, i.e., π(1000) = 168.

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

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