Explain why3 x 5 x 7 + 7 is a

We have, $\quad 3 \times 5 \times 7+7=105+7=112$

Now, $112=2 \times 2 \times 2 \times 2 \times 7=2^{4} \times 7$

So, it is the product of prime factors 2 and 7. i.e., it has more than two factors.

Hence, it is a composite number.