Let be a positive integer and
 = () be the digit sum of such that
 + 1 ≡ 0 (mod 2).
Is it that if is prime then is also prime?


e.g. =47(prime)-> =4+7=11 (prime)



Digit sum of a prime number
Not necessarily, but it takes a while to see this, because
you're not allowing $q$ to be a multiple of $2$, and it cannot be
a multiple of $3$ (other than $3$ itself) because then the same
would be true of $p$. So the smallest candidate for $q$ is $25$,
which happens for the first time at $p=997$.


