Results for “what are prime numbers” · retrieved September 22, 2026

Quick answer

A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

A prime number is a natural number greater than 1 that has exactly two distinct positive divisors: 1 and itself. Because they cannot be formed by multiplying smaller natural numbers, primes are often described as the multiplicative building blocks of all natural numbers. According to the fundamental theorem of arithmetic, every natural number greater than 1 is either a prime itself or can be uniquely factorized into a product of prime numbers. Numbers greater than 1 that are not prime are called composite numbers. The number 2 is the smallest prime and the only even prime number.

Answer details

1

Definition and Factors

A prime number must be greater than 1 and have exactly two factors: 1 and the number itself. If a number has more than two factors, it is classified as a composite number.

2

Fundamental Theorem of Arithmetic

Primes are considered the building blocks of natural numbers because every integer greater than 1 can be uniquely expressed as a product of prime numbers.

3

The Role of 2

The number 2 is the smallest prime number and the only even prime. All other even numbers are composite because they are divisible by 2.

4

The Status of 1

The number 1 is neither prime nor composite. It is excluded from the definition of prime numbers to ensure that the fundamental theorem of arithmetic remains valid.

en.wikipedia.org

Prime number

A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 4 is composite because it is a product (2 × 2) in which both numbers are smaller than 4. Primes are central in number theory because of

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britannica.com

Prime number

prime, any positive integer greater than 1 that is divisible only by itself and 1—e.g., 2, 3, 5, 7, 11, 13, 17, 19, 23, …....A key result of number theory, called the fundamental theorem of arithmetic(see arithmetic: fundamental theory), states that every positive integer greater than 1 can be expressed as the product of prime numbers in a unique fashion. Because of this, primes can be regarded as the multiplicative “building blocks” for the natu

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mathworld.wolfram.com

Prime Number -- from Wolfram MathWorld

Prime Number A prime number (or prime integer, often simply called a "prime" for short) is a positive integer that has no positive integer divisors other than 1 and itself. More concisely, a prime number is a positive integer having exactly one positive divisor other than 1, meaning it is a number that cannot be factored. For example, the only divisors of 13 are 1 and 13, making 13 a prime number, while the number 24 has divisors 1, 2, 3, 4, 6,

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encyclopediaofmath.org

Prime number

Prime number 2020 Mathematics Subject Classification: Primary: 11A41 [MSN][ZBL] A natural number (positive integer) $ p > 1 $ that has only the two divisors 1 and $ p $. E.g., $$ 2 , 3 , 5 , 7 , 11 , 13 , 17 , 19 , 23 , 29 , 31 , . . . . $$...Natural numbers which are not prime are called composite. The concept of a prime number is fundamental in the study of divisibility of natural numbers. Thus, the fundamental theorem of elementary number th

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khanacademy.org

Prime numbers (video)

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britannica.com

Prime numbers

Prime number The number 7 is a prime number, meaning it can be divided only by 1 and itself. (more)...Prime numbers are simple to define but have endless complexity....A prime number is any number that can be divided only by 1 and itself. For example, 3 is a prime number because the only numbers that divide it are 1 and 3. The number 4 is not, because it can be divided by 1, 2, and 4. The prime numbers are sometimes called the chemical elements o

June 13, 2025

math.libretexts.org

1.2: Definitions - Prime Numbers - Mathematics LibreTexts

Consider the definition of a prime number....Definition: Prime Number...A prime number is a positive integer, greater than \(1\), whose only factors are \(1\) and itself....You probably first heard this...in Middle School, if not earlier. It is a perfectly valid definition of what it means for an integer to be prime. In more advanced mathematics, it was found that it was necessary to define a notion of primality for objects other than integ

May 8, 2019

youtube.com

What are Prime Numbers? | Math with Mr. J

Welcome to Math with Mr. J. In this video, I'm going to cover what prime numbers are. Now, prime numbers are whole numbers with only two factors, one and the number itself. So, we're going to go through a few examples of prime numbers to better understand that, and then take a look at five other numbers and determine if they are prime or not prime. So, let's jump into our first example of three. Now, three is a whole number, so we need to take a

September 22, 2021

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