The book is now available! 9091
(another Prime Pages' Curiosity)
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+ A unique prime indeed. Reverse the order of its middle digits to form the next unique prime (9901).

+ The greatest prime factor of any 10-digit repdigit is 9091. [La Haye]

+ The smallest prime of the form 10k-10^(k-1).....+10^0, for k=4. [Silva]

+ 9091, 909091, 909090909090909091, and 909090909090909090909090909091 are each prime, and 9091 and 909091 are the two smallest prime factors of 9090909090909090909090909090909091. Submitted on 9/09/09. [Green]

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

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