Prime numbers definition:

A prime number is a natural number that can be divided evenly only by one and itself, and it is greater than one.

So which numbers are called prime numbers?

Numbers are called prime numbers if

1. the number is natural;

2. the number is greater than one;

3. the number can be divided evenly only by one and itself.

2. the number is greater than one;

3. the number can be divided evenly only by one and itself.

Note, only natural numbers can be prime numbers.

Now we know which numbers are called prime numbers and we can give examples of prime numbers.

Examples of prime numbers:

2; 3; 5; 7; 11; 13; 17; 19; 23; 29; 31;...

All of these numbers are natural, greater than one and can be divided evenly only by one and itself.

So you see, mathematical definition of a prime number is very simple.

Prime numbers are often called primes.

Now the question: is 4 a prime number?

No, four is not a prime number because it can be divided evenly by one, by itself and by two.