A prime number is a number that is only divisible by 1 and itself.

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Determine if a number is prime without using arithmetic [duplicate]

Write a program which determines if a given number is prime. The catch: No digits or arithmetical operators. This means: No digits from 0 to 9, anywhere in the program, and whatever the meaning No ...
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27answers
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Calculate prime gaps

Finding primes is a programming rite of passage and very frequently a first serious program someone crates (usually with trial division). But primes alone are already worn out. A next far more ...
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11answers
701 views

Find the smallest prime from a substring

In 1946 Erdos and Copeland proved that a certain number is a normal number, i.e. the digits in its decimal expansion are uniformly distributed. Users will input a sequence of digits and you will find ...
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8answers
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Is it a prime? w/o math

Write a program or function in any language that tells if the input is a prime number. The input is a string representing a natural number in base-10. The output is one of the two strings "Prime" or ...
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24answers
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Goldbach's conjecture

Write a program that prompts the user for an even integer greater than 2. Given Goldbach’s conjecture that every even integer greater than 2 can be expressed as the sum of two primes, print out two ...
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4answers
117 views

Quine with prime sourcecode character distribution constraints

Your program should take no input, and no network or other connections. Your program should output it's sourcecode. The sourcecode must consist of 3 types of characters: Numeric (0-9), Alpha ...
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10answers
473 views

Circular primes

Given a number determine if it is a circular prime. A circular prime is a prime where if you rotate the digits you still get prime numbers. 1193 is circular prime because 1931 and 9311 and 3119 are ...
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5answers
319 views

Enumerate the primes using only unary arithmetic

Write a program which prints the sequence of prime numbers. The shortest solution wins! All numbers must have a unary representation (not just in the output, but throughout the entire program). This ...
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7answers
331 views

Nth K-Ugly Number

Write the shortest code in any language of your choice to find the Nth K-ugly number. A K-ugly number is a number whose only prime factors are the prime numbers <= K. This K-ugly number is ...
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0answers
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Fastest way to generate Smarandache–Wellin number [duplicate]

Given a number n find the Smarandache–Wellin number for n. Ex: for n=2 output=23 for n=5 output=235711 Answer it in ruby or python. given constraints are n<=70000
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19answers
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Give the smallest number that has N divisors

Your function takes a natural number and returns the smallest natural number that has exactly that amount of divisors, including itself. Exemples: f(1) = 1 [1] f(2) = 2 [1, 2] f(3) = 4 [1, 2, 4] ...
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6answers
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Find largest prime which is still a prime after digit deletion

Over at http://math.stackexchange.com/questions/33094/deleting-any-digit-yields-a-prime-is-there-a-name-for-this the following question is asked. How many primes are there that remain prime after you ...
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2answers
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Fastest code to find the next prime

The problem is as follows. Input: An integer n Output: The smallest prime bigger than n. The challenge is to give the fastest code possible to do this. I will test the code on values starting at ...
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2answers
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Fastest semiprime factorization

Write a program to factorize a semi-prime number in the shortest amount of time. For testing purposes, use this: 38!+1 (523022617466601111760007224100074291200000001) It is equal to: ...
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2answers
308 views

List ALL prime-factorized natural numbers in ANY order

This is a variant of List prime-factorized natural numbers up to N in ascending order, but the solutions can be very different. Write a program that outputs prime factorizations of all natural ...
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2answers
632 views

List prime-factorized natural numbers up to N in ascending order

For a given n list prime factorization of all natural numbers between 1 and n in ascending order. For example, for n = 10 the output would be: 1: 2: 2^1 3: 3^1 4: 2^2 5: 5^1 6: 2^1 3^1 7: 7^1 8: 2^3 ...
6
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9answers
960 views

Find the nth Fibonnaci Prime, in the shortest code

The challenge is rather simple: Take a positive whole number n as input. Output the nth Fibonacci prime number. Input can be as an parameter to a function (and the output will be the return ...
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3answers
401 views

Prime tester + nth-prime finder (TO BE CLOSED) [duplicate]

Possible Duplicate: List of first n prime numbers most efficiently and in shortest code This is to be closed soon - please don't answer (mod- please close!) This challenge is to write the ...
5
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8answers
493 views

Square-free semiprime counting

Definition A square-free semiprime is a natural number that is the product of two distinct prime numbers. The task Given a natural number n, count all square-free semiprimes less than or equal ...
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24answers
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Sexy Primes — codegolf

Write the shortest code to print sexy primes till n Sexy Primes are pairs of numbers (n, m) such as n and m both are prime, and m = n + 6. EDIT Modifying the question a little bit after reading ...
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9answers
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List of first n prime numbers most efficiently and in shortest code

Rules are simple: First n primes (not primes below n), should be printed to standard output separated by newlines (primes should be generated within the code) primes cannot be generated by an ...
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30answers
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List of primes under a million

This is my first code golf question, and a very simple one at that, so I apologise in advance if I may have broken any community guidelines. The task is to print out, in ascending order, all of the ...
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7answers
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Sum of (at most) 5 primes

Terence Tao recently proved a weak form of Goldbach's conjecture! Let's exploit it! Given an odd integer n > 1, write n as a sum of up to 5 primes. Take the input however you like, and give ...
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10answers
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Return the first N primes

With a twist; your algorithm has to be less complex than O(X2) where X is the Nth prime. Your solution post should include the character count and the theoretical complexity in terms of X (or N, which ...
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2answers
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Numbers that are divisible by at least three different primes [closed]

I was studying different sequences related to prime numbers and came across this sequence: A000977: Numbers that are divisible by at least three different primes. Write code to find the n-th number ...
3
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5answers
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Show Ulam's spiral

Similar to this but in this one you need to write spiral starting from the center where: space means composite number .(dot) means prime number. Size of the spiral can be given as parameter or on ...
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1answer
684 views

Find 10 large prime numbers with n digits

You are given n (200 ≤ n < 250) as a command line argument. Print 10 prime numbers with n digits. Your program should run under 1s and must be shorter than 5000 bytes (excluding). Sum the ...
6
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2answers
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The Prime Grid Game

I had fun solving this, so i offer this golf challenge. The objective of this golf is to find the largest prime number that can be constructed using the given instructions. You should accept 3x3 ...
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4answers
666 views

Code-Challenge:The Nearest Prime

Challenge In this task you would be given an integer N you have to output the nearest prime to the integer. If the number is prime itself output the number. The input N is given in a single ...
8
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13answers
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Factorize me!!!

In this task, you have to write a program, that computes the prime factors of a number. The input is a natural number 1 < n < 2^32. The output is a list of the prime factors of the number in the ...
8
votes
6answers
578 views

What is the average of n, the closest prime to n, the square of n and the closest fibbonacci number to n?

This is a math problem which takes quite many things into question, making it rather challenging, and as you might have guessed, it's a code golf, so it should be as short as possible as well. The ...
7
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18answers
640 views

Find prime factors [duplicate]

A whole program to find the prime factors of a given number. The number will be given on standard input.
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25answers
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Sum of primes between given range

Write the shortest code for finding the sum of primes between a and b (inclusive). Input a and b can be taken from command line or stdin (space seperated) Assume 1 <= a <= b <= 108 ...