Tool to check if a number is a prime number. A primality test is a mathematical and algorithmic test that indicates whether a number is prime or compound and answers true or false.

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Tool to check if a number is a prime number. A primality test is a mathematical and algorithmic test that indicates whether a number is prime or compound and answers true or false.

Answers to Questions

How to know if a number is a prime?

To know if a number is prime, it need to check if it has any divisor except 1 or itself, this test is called a primality test.

Example: Is 23456789 a prime number ? True

Example: Is 123456789 a prime number ? False

What are primality tests algorithms?

It exists several test to know if a number is a prime number : Miller–Rabin or Lucas-Lehmer are the one used by dCode.

What is the prime numbers test algorithm?

The algorithm tries all or almost all numbers (it avoids even numbers and multiples of 3). Here is a pseudo code applicable for prime numbers not too large: function is_prime(n) { if n ≤ 1 return FALSE else if n ≤ 3 return TRUE else if (n mod 2 = 0) or (n mod 3 = 0) return FALSE i = 5 while (i*i ≤ n) { if (n mod i = 0) or (n mod (i + 2) = 0) return FALSE i = i + 6 } return TRUE

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Source code

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