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Every number greater than 161 is the sum of distinct primes of the form 6n - 1. [Wells]
The smallest semiprime that yields a palindromic prime when turned upside down. [Ondrejka]
Palindromic semiprime s is the only solution as a quadratic
residue modulo n=10^3 for two CONSECUTIVE primes p, q (out
of 2^3*3*7 primes < 10^3): p = 619 and q = p + 2^2*3 =
631, i.e., 619^2 = s (mod n) = 631^2. Note that (a) p and q are
consecutive irregular primes, p+3, q+3 consecutive
semiprimes. (b) Only one such solution modulo n=10^2 (there
are 5^2 primes < 10^2): p = 47 and p + 2*3 = 53. [Krug]
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