What numbers are only divisible by 1?
All multiples of 1, which is an infinite number.
If your talking about prime numbers, prime numbers are numbers that are only divisible by one and themselves. Composite numbers are numbers divisible by more than one and itself. Like 3 is prime because it is only divisible by 1 and itself. 6 is composite because it is divisible by 1,2,3, and itself.
Composite numbers are numbers which are divisible by another number other than 1 and the number itself. Ex 1: 15 is divisible by 1, 3, 5 and 15. So, 15 is a composite number. Ex 2: 3 is divisible by 1 and 3 only. So, such numbers which are only divisible by 1 and the number itself are known as Prime numbers.