Number Theory
Prime Numbers
What is the next prime number in this sequence:
\[2, 3, 5, 7, 11, 13, \underline{\quad}, \ldots ? \]
True or false: the number \( 47 \) is prime.
Which of the following numbers is prime?
\[A, \hspace{0.5cm} A+2, \hspace{0.5cm} A+4\]
If \(A>3,\) can all three numbers above be prime?
True or false: the number \( 21 \) is prime.