They are all the numbers that have only two factors which are themselves and one whereas composite numbers have more than two factors.
show me a multiplication chart
The answer depends on how the numbers are combined: addition, subtraction or multiplication.
That they are not perfect squares.
It is the identity element of multiplication. That puts it in a special category.
Sure, you can make a multiplication chart that is any size you want.
Only in the ones column. Prime numbers aren't multiples of anything but one and themselves.
You can find a great multipication chart on google imiges just type in multiplication chart and it will give you lots of great multiplication chats.