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Formula
A prime number has exactly two divisors: 1 and itself
Worked example
97 is prime. 84 = 2 × 2 × 3 × 7.
Frequently asked questions
Is 1 a prime number?
No. A prime has exactly two different divisors, and 1 has only one.
Is 2 prime?
Yes, it is the only even prime.
How many primes are there?
Infinitely many, as Euclid proved.
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Results are estimates for information only. Check important figures with a professional.