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.

Primality Test - dCode

Tag(s) : Arithmetics

dCode is free and its tools are a valuable help in games, puzzles and problems to solve every day!

You have a problem, an idea for a project, a specific need and dCode can not (yet) help you? You need custom development? *Contact-me*!

Sponsored ads

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.

To know if a number is prime, check if it has any divisor except 1 or itself, this test is called a primality test. The test first uses probabilistic algorithms and if the probability of being prime is non-zero, the algorithms become deterministic (careful verification of potential divisors).

Example: Is 23456789 a prime number ? True

Example: Is 123456789 a prime number ? False

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

It is mainly a mathematical convention that avoids many problems in mathematical definitions and theorems (where one would have to exclude 1 or treat it as a special case). Another advantage is that the prime factor decomposition is unique 6 = 2*3 and not 1*2*3 or 1*1*1*2*3.

The deterministic 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: `// pseudo-code`

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

dCode retains ownership of the source code of the script Primality Test online. Except explicit open source licence (indicated Creative Commons / free), any algorithm, applet, snippet, software (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any function (convert, solve, decrypt, encrypt, decipher, cipher, decode, code, translate) written in any informatic langauge (PHP, Java, C#, Python, Javascript, Matlab, etc.) which dCode owns rights will not be given for free. To download the online Primality Test script for offline use on PC, iPhone or Android, ask for price quote on contact page !

primality,number,prime,test,check

Source : https://www.dcode.fr/primality-test

© 2019 dCode — The ultimate 'toolkit' to solve every games / riddles / geocaches. dCode

Feedback