The book is now available! 169
(another Prime Pages' Curiosity)
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+ 169 = (27 + 72) - (7 + 1) and is the smallest perfect square of the form (2p + p2) - (p + 1). [Charles]

+ The smallest square that is prime when turned upside down. [Wu]

+ 169 is the first composite Pell number with a prime index. Coincidentally, it is also the last square in the Pell sequence. [Axoy]

+ The sum of first 12 powers of semiprimes is (12+1)^2. [Post]

+ The sum of first five emirps can be represented as the square of the first emirp. [Loungrides]

(There are 4 curios for this number that have not yet been approved by an editor.)

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