Math & Algebra Tool
Prime Numbers Chart
Visual grid of prime numbers up to 100.
Primes 1-100
Prime Composite
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What is a Prime Number?
A prime number is a whole number greater than 1 whose only factors are 1 and itself. A factor is a whole number that can be divided evenly into another number.
Frequently Asked Questions
What is a prime number?+
A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. It has exactly two factors: 1 and itself.
Is 1 a prime number?+
No. By definition, a prime number must have exactly two distinct factors. The number 1 only has one factor (itself), so it is not prime. It is called a unit.
What is the only even prime number?+
2 is the only even prime number. All other even numbers are divisible by 2, making them composite. For example, 4 is divisible by 1, 2, and 4.
How many primes are there between 1 and 100?+
There are 25 prime numbers between 1 and 100. This chart highlights all of them in blue.
What is the Sieve of Eratosthenes?+
It's an ancient algorithm for finding all prime numbers up to a limit. You list the numbers, circle 2, and cross out all multiples of 2. Then circle the next available number (3) and cross out its multiples, and so on.
Are there infinite prime numbers?+
Yes, this was proved by Euclid around 300 BC. No matter how high you count, you will always find another prime number, though they become less frequent.