85

This number is a composite.

+ (8511 - 85)/11 ± 1 are twin primes. [Luhn]

+ Between 641 and 114689 (the second smallest Fermat divisor) there exist 85 prime numbers that could conceivably be Fermat divisors.

+ There are 85 five-digit primes that begin with 85. [Bopardikar]

+ The only composite number resulting from the sum of three double-digit consecutive emirps, 17, 31, 37. Note that the ordered concatenation of these emirps, i.e., 173137 is prime. [Loungrides]

+ The only known Smith number n such that the aliquot sum of n = π(n). [Gupta]

(There are 2 curios for this number that have not yet been approved by an editor.)

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