The number one is neither prime nor composite. Prime numbers are those defined as natural numbers greater than one not divisible by any other numbers but one and itself. Composite numbers have at least one additional positive divisor and include all whole numbers greater than one that are not prime.
Since 11 is only divisible by one and 11, it is a prime number. In contrast, not only is 12 divisible by one and itself, but also by two, three, four and six, so it is composite. The first 10 prime numbers, in order, are two, three, five, seven, 11, 13, 17, 19, 23 and 29.