518

Number
$518$ (five hundred and eighteen) is:
 * $2 \times 7 \times 37$


 * The $4$th integer after $0$, $1$, $2$ such that its double factorial plus $1$ is prime:
 * $518!! + 1$ is prime


 * The $11$th even integer after $2$, $4$, $94$, $96$, $98$, $400$, $402$, $404$, $514$, $516$ that cannot be expressed as the sum of $2$ prime numbers which are each one of a pair of twin primes


 * The $14$th number after $0$, $1$, $2$, $3$, $4$, $5$, $6$, $7$, $8$, $9$, $89$, $135$, $175$ which is the sum of the increasing powers of its digits taken in order:
 * $5^1 + 1^2 + 8^3 = 518$


 * The $40$th untouchable number after $2$, $5$, $52$, $88$, $96$, $120$, $124$, $\ldots$, $324$, $326$, $336$, $342$, $372$, $406$, $408$, $426$, $430$, $448$, $472$, $474$, $498$, $516$


 * The $49$th noncototient after $10$, $26$, $34$, $50$, $\ldots$, $386$, $394$, $404$, $412$, $436$, $466$, $470$, $474$, $482$, $490$:
 * $\nexists m \in \Z_{>0}: m - \map \phi m = 518$
 * where $\map \phi m$ denotes the Euler $\phi$ function

Also see