What are prime numbers?
Prime numbers are a fundamental concept in number theory, a branch of mathematics. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. Thus, the first few prime numbers are 2, 3, 5, 7, 11, 13, 17, and so on.
Properties and theories related to prime numbers

Fundamental Theorem of Arithmetic: This theorem states that every number greater than 1 can be uniquely written as a product of prime numbers. This is also called the prime factorization of a number.

Prime numbers are unlimited: There are infinitely many prime numbers. This was proven by the ancient Greek mathematician Euclid more than two millennia ago.

Distribution of prime numbers: The "Prime Number Theorem" provides insight into how prime numbers are distributed. It states that, as numbers get larger, the chance that a randomly selected number is prime is roughly inversely proportional to the number of digits in that number.

Twin prime numbers: These are pairs of prime numbers that are exactly two numbers apart, such as (11, 13) or (17, 19). It is an open question whether there are infinitely many of these pairs.

Cryptography: Prime numbers play a crucial role in modern cryptography. The RSA algorithm, one of the first practically usable publickey cryptosystems, for instance, uses the fact that it is hard to factorize the product of two large prime numbers.

Mersenne primes: These are prime numbers that are one less than a power of two. They are named after the French monk Marin Mersenne, who encouraged the study of these numbers in the early 17th century.
Although prime numbers are simple to define, they are incredibly complex in their behavior and distribution, and many questions about prime numbers remain unanswered in mathematics. There are large prizes available for those who can solve certain problems related to prime numbers, such as proving the Riemann hypothesis, which describes the distribution of the prime numbers.