How to enter an international number?

On my iphone, how would I type into a new message an american number, do i have to put in the brackets? And how many numbers long is an american number. I'm in the uk.

1 is the country code for the US, and US phone numbers are 10 digits. You don't enter the brackets, they separate the area code from the rest of the number. In most parts of the US, if a number is in the same area code, you only need the last 7 digits, but from outside the US you always need all 10.