The factors of the number 37 are 1 and 37. This makes the number 37 a prime number, by definition. A prime number is any number that can be divided by only the number itself and the number 1.
If a number is not a prime number, it is a composite number. A composite number is any positive number that has at least one more number it can be evenly divided by other than the number 1 and itself.
Prime numbers are the building blocks of all other numbers, because prime numbers are multiplied together to define the other numbers.