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991, 99991, and 9999991 are each prime. [Avrutin]
This number, as well as 331 and 661, are all prime. Note that the product of these three primes is a Carmichael Number. [Patterson] The largest threedigit permutable prime. 991^2 = 982081 and 982 + 0 + 8 + 1 = 991. [Meller] Florida angler Allen Ogle caught a 991pound Hammerhead Shark on May 30, 1982.
(There are 4 curios for this number that have not yet been approved by an editor.)
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