The book is now available! 25
(another Prime Pages' Curiosity)
Prime Curios!
Curios: Curios Search:

The nth Prime Page will now find any of the first 2.623˙1015 primes or π(x) for x up to 1017.

+ 25 is a strong pseudoprime base 2 + 5. [Gupta]

+ The only prime square whose digits are all prime.

+ 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]

+ pi(100) = 25.

+ There are exactly 52 squares less than or equal to 10002 that are the sum of twin prime pairs. [Honaker]

+ 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.

+ There are exactly 25 (a perfect square) primes beginning with the digit 1 among primes smaller than one thousand. It's more than for the other digits. [Capelle]

+ The smallest composite number whose prime factors are written with its digits. [Capelle]

+ 25^5+52^2 is a 2+5-digit prime. [Silva]

+ A prime square whose prime count pi(5^2) is another prime square (3^2) and it's prime count is another prime square (pi(pi(5^2)) = 2^2). [Picheny]

(There are 5 curios for this number that have not yet been approved by an editor.)

  To link to this page use /curios/page.php?number_id=392

Prime Curios! © 2000-2016 (all rights reserved)