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Chris K. Caldwell <email@example.com>
25 is a strong pseudoprime base 2 + 5. [Gupta]
The smallest two-digit number N = ab such that the sum and absolute difference of its digits along with the concatenations of each in both directions are all prime. E.g., 5 - 2 = 3, 5 + 2 = 7, 37, and 73 are prime. [Heleen]
25 is the concatenation of 2 and 5 which are the only primes of the form 10n + 2 and 10n + 5. Note that 25 = 52. [Murthy]
Laura Nickel, a high school student when she made international news by codiscovering the 25th Mersenne prime, is now Ariel Glenn.
25^5+52^2 is a 2+5-digit prime. [Silva]
A prime square whose prime count (5^2) is another prime square (3^2) and it's prime count is another prime square (((5^2)) = 2^2). [Picheny]
(There are 5 curios for this number that have not yet been approved by an editor.)
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