What is a defining feature of prime numbers?

A defining feature of prime numbers is that they can only be divided evenly by one and themselves. This definition establishes prime numbers as unique in the set of natural numbers, specifically because they cannot be formed by multiplying two smaller natural numbers. For example, the number 5 is considered prime because its only divisors are 1 and 5. This characteristic is fundamental in number theory, as prime numbers serve as building blocks for all other natural numbers through multiplication.

In contrast, the other options do not accurately describe prime numbers. The first option mentions that prime numbers have more than two factors, which is incorrect since prime numbers have precisely two distinct positive factors. The second option suggests that prime numbers can be negative, but prime numbers are defined only within the context of positive integers. Lastly, the assertion that prime numbers always include zero is false, as zero is not classified as a prime number. Therefore, the correct answer highlights the essential property that defines prime numbers.