The following is an encore presentation of everything everywhere daily.

Prime numbers are considered to be the building blocks of mathematics.

Every natural number can be broken down into the constituent prime numbers that make it up.

Prime numbers have been known since antiquity and they're one of the simplest aspects of mathematics to understand.

Yet they remain at the center of some of the most puzzling problems in mathematics today.

Learn more about prime numbers, what we know about them, and what we don't know, on this episode of

Everything Everywhere Daily. A prime number is a number is a really simple concept, so simple that it's one of the

first mathematical concepts that was known to the ancients.

A prime number is simply a number that is only divisible by itself and one.

Any number that is not prime is called a composite number.

And one is considered to be neither prime nor composite.

So for example, two, three, five, seven and 11 are all prime numbers.

Two is the only even prime number as all even numbers are divisible by two. The first text we know of

that references prime numbers is mathematical text from ancient Egypt which

dates back to the year 1550 BC. The first person to explicitly talk about prime numbers as prime numbers was the ancient Greek mathematician Euclid.

Euclid proved two important theorems that are central to prime numbers.

The first was that there are an infinite number of prime

numbers. This is actually pretty easy to prove so I'll just do it right here. Assume for a moment

that there are only a finite number of primes. If you multiply all the primes together and add one, you have a number

that is not evenly divisible by any other prime number. Hence, it must be a prime number.

Because the original stipulation was that the number of primes was finite

and we used them all, you found another that wasn't. So the number of primes is infinite.

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