Question

Show that $11 \times 19 \times 23 + 3 \times 11$ is not a prime number.

Answer 1

Factor out the common term $11$ from the expression:

$$11 \times 19 \times 23 + 3 \times 11 = 11(19 \times 23 + 3)$$

Now simplify the expression inside the parentheses:

$$19 \times 23 = 437$$

$$437 + 3 = 440$$

Thus, the expression becomes:

$$11 \times 440 = 4840$$

Since $4840$ is divisible by $11$, it is not a prime number.