19

This number is a prime.

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The only prime of form p^3-q^3, where p, q are primes, i.e., 3^3-2^3. [Loungrides]

(11, 13, 17, 19) is the first prime quadruple (p, q, r, s) such that s divides pqr+1. [Loungrides]

The only known prime p of form 4*q+7, where q and 4*p+7 are prime. [Loungrides]

The first prime of form (pqrs-1)/t where p, q, r, s, t are consecutive primes, case (2, 3, 5, 7, 11). Note that it is the only known prime of this form. [Loungrides]

There are 19 distinct-odd-digit emirp pairs. [Loungrides]

5^19 is the smallest pandigital number of form p^q where p is a prime digit, i.e., 5^19=19073486328125. [Loungrides]

The smallest Loeschian prime of form x^2+x*y+y^2, where x, y are successive primes, case (x=2, y=3), i.e., 2^2+2*3+3^2=19. [Loungrides]