Say the number is expressed in the form $10a+b$. We want to find all numbers such that $10a+b-7a-7b=3a-6b$ is prime. Note that we can factor out $3$ from this expression to get $3(a-2b)$. The only way for this to be prime is if $a-2b=1$. Checking all the values of $b$ from $0$ to $9$, the only values of $b$ that work are $0,1,2,3,$ and $4$. The corresponding $a$ values for this are $1,3,5,7,$ and $9$. This means the answer is $\boxed{10,31,52,73,94}$.

Say the number is expressed in the form $10a+b$. We want to find all numbers such that $10a+b-7a-7b=3a-6b$ is prime. Note that we can factor out $3$ from this expression to get $3(a-2b)$. The only way for this to be prime is if $a-2b=1$. Checking all the values of $b$ from $1$ to $9$, the only values of $b$ that work are $1,2,3,$ and $4$. The corresponding $a$ values for this are $3,5,7,$ and $9$. This means the answer is $\boxed{31,52,73,94}$.

Say the number is expressed in the form $10a+b$. We want to find all numbers such that $10a+b-7a-7b=3a-6b$ is prime. Note that we can factor out $3$ from this expression to get $3(a-2b)$. The only way for this to be prime is if $a-2b=1$. Checking all the values of $b$ from $1$ to $9$, the only values of $b$ that work are $1,2,3,$ and $4$. The corresponding $a$ values for this are $3,5,7,$ and $9$. This means the answer is $\boxed{31,52,73,94}$.