The number 37 is a prime number. The definition of a prime number is any positive number that can only be divided by the number one or itself. A prime number must also be a whole number larger than the value of one.
In general, if a positive, whole number is not a prime number, it could be a composite number. A composite number is one that has at least one other number that can be equally divided into it, other than the number one and itself.
The mathematical property of determining if a number is a prime or not is called primality.