168
(another Prime Pages' Curiosity)
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+ The number of primes less than or equal to a thousand (pi(1000) = 168) equals the number of hours in a week (7 x 24 = 168). [Honaker]

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



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