\newchapter{Prime numbers}

Prime numbers are the numbers which has no divisors except itself and 1.
This can be represented graphically.

Let's take 9 balls or some other objects. 9 balls can be arranged into rectangle:

\begin{lstlisting}
ooo
ooo
ooo
\end{lstlisting}

So are 12 balls:

\begin{lstlisting}
oooo
oooo
oooo
\end{lstlisting}

Or:

\begin{lstlisting}
ooo
ooo
ooo
ooo
\end{lstlisting}

So 9 and 12 are not prime numbers. 7 is prime number:

\begin{lstlisting}
ooooooo
\end{lstlisting}

Or:

\begin{lstlisting}
o
o
o
o
o
o
o
\end{lstlisting}

It's not possible to form a rectangle using 7 balls, or 11 balls or any other prime number.

The fact that balls can be arranged into rectangle shows that the number can be divided by the number which is represented by height and width of rectangle.
Balls of prime number can be arranged vertically or horizontally, meaning, there are only two divisors: 1 and the prime number itself.

\leveldown{}

\input{prime/factorize}
\input{prime/coprime}
\input{prime/semiprime}
\input{prime/RSA}

\levelup{}

