Prime Numbers Chart and List

A prime number has exactly two factors: 1 and itself. The primes below 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97, which is 25 primes. Tap any number on the chart to see its factors.

How the Sieve of Eratosthenes works

1. Write the numbers from 2 up to your limit.
2. Circle 2 and cross out every multiple of 2.
3. Move to the next number not crossed out (3), circle it and cross out its multiples. Start crossing at its square, 9, because smaller multiples are already gone.
4. Stop once the next prime squared is larger than the limit. Everything not crossed out is prime.

Facts about primes

• 2 is the only even prime.
• 1 is not prime: it has only one factor.
• There are infinitely many primes (Euclid’s proof).
• Every whole number above 1 is a product of primes in exactly one way (the fundamental theorem of arithmetic).
• There are 168 primes below 1,000.

Twin primes

Twin primes differ by 2, like 11 and 13 or 59 and 61. Nobody has proved whether there are infinitely many; it is one of the famous open problems in mathematics.

Prime Numbers Chart and List quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

What are the prime numbers from 1 to 100?

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.

Why is 1 not a prime number?

A prime must have exactly two different factors. 1 has only one, and excluding it keeps prime factorizations unique.

What is the largest known prime?

The record primes are Mersenne primes (2ᵖ − 1) found by the GIMPS project; they have tens of millions of digits.

How do I check if a big number is prime?

Try dividing by primes up to its square root. The checker on this page does it instantly up to 1 trillion.

What is a composite number?

A whole number above 1 that is not prime, like 12 = 2 × 2 × 3.

Sources

• Wolfram MathWorld: Prime Number
• The Prime Pages (University of Tennessee at Martin)

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