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Check if a number is prime, find all primes in a range, and get the prime factorization of any number. Free online tool with instant results.
A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. Primes are the building blocks of all integers through the Fundamental Theorem of Arithmetic.
Check whether a number is prime.
| Range | Count | Largest |
|---|---|---|
| 1–100 | 25 | 97 |
| 1–1,000 | 168 | 997 |
| 1–10,000 | 1,229 | 9,973 |
| 1–100,000 | 9,592 | 99,991 |
| 1–1,000,000 | 78,498 | 999,983 |
Formula
Trial Division: test divisibility by all integers from 2 to √nn = the number being tested for primality
√n = only need to check divisors up to the square root
Worked Example
Is 97 prime?
Did you know? The largest known prime number (as of 2024) is 2^136,279,841 − 1, a Mersenne prime with over 41 million digits, discovered by the Great Internet Mersenne Prime Search (GIMPS).
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