Multiplying prime numbers If I multiply $13$ and $17$ to get $221$ I can only get $221$ by multiplying $13$ and $17$ (excluding $1$ and $221$) does the same rule apply to multiplying $3$ numbers? (excluding the use of $1$)

If you mean multiplying 3 prime numbers, then yes there is only one way (this is known as the fundamental theorem of arithmetic). 
For instance $715=5\cdot 11\cdot 13$, and only these three primes will produce it (if you exclude $715=(-5)\cdot (-11)\cdot 13$ and so on)
