Question

7×11×13+13 it is prime or composite

Answer 1

it is composite number
$7 \times 11 \times 13 + 13 \\ 13(7 \times 11 \times 1 + 1) \\ 13(7 7 + 1) \\ 13 \times 78$
so this number have more than 2factors(1,13,78)

Answer 2

7×11×13+13=13(7×11+1)=13(77+1)=13×78

It is clearly, a composite number.