# All Questions

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12answers
1k views

### Find the Emirps!

An emirp is a non-palindromic prime which, when reversed, is also prime. The list of base 10 emirps can be found on OEIS. The first six are: ...
9answers
936 views

### Base Conversion With Strings

Introduction We've have a few base conversion challenges here in the past, but not many designed to tackle arbitrary length numbers (that is to say, numbers that are long enough that they overflow ...
3answers
839 views

### Crazy but Rational Bases

We have many challenges based on base 10, base 2, base 36, or even base -10, but what about all the other rational bases? Task Given an integer in base 10 and a rational base, return the integer in ...
20answers
3k views

### Is this a three-digit number ending in one?

Given a nonnegative integer, return whether it is a three digit number ending in one, in any consistent integer base. In other words, the number needs to be represented in base-N, N being an integer ...
18answers
1k views

### Digital Diversity

A positive integer may be represented in an integer base 1 <= b < inf. When converted to that base it has some number of distinct digits. Any positive ...
7answers
2k views

### Mixed Base Conversion

Background Most people on here should be familiar with several base systems: decimal, binary, hexadecimal, octal. E.g. in the hexadecimal system, the number 1234516 would represent ...
19answers
1k views

### Reverse and square

In this challenge you will compute numbers from a curious sequence. Your input is a single decimal nonnegative integer. Reverse the bits in this integer and then square the number to get the required ...
2answers
1k views

### Residue Number System

In the vein of large number challenges I thought this one might be interesting. In this challenge, we will be using the Residue Number System (RNS) to perform addition, subtraction, and ...
20answers
820 views

### Decompose a number!

Your task is to decompose a number using the format below. This is similar to base conversion, except that instead of listing the digits in the base, you list the <...
5answers
431 views

### Print a table of numbers in decimal and 2**i bases

Computers live by binary. All programmers know binary. But the 2**x bases are often neglected as non-practical, while they have beautiful relations to binary. To ...
12answers
999 views

### Last Nonzero Digits of a Factorial in Base

You should write a program or function which given three positive integers n b k as input outputs or returns the last k digits ...
10answers
1k views

### Is it really a comcoin?

Very interesting background Comcoins are a currency like any other. The residents of Multibaseania (an economically robust system of city-states with very few residents in a galaxy far, far away) use ...
2answers
2k views

### Standardise a Phinary Number

Background Most people on here should be familiar with a few integer base systems: decimal, binary, hexadecimal, octal. E.g. in the hexadecimal system, a number abc.de16 would represent ...
1answer
264 views

### Find a numeric coincidence when representing numbers in various bases

Recently, when doing some code-golf challenge, I came up with with two solutions, in 69 and 105 bytes. It's a remarkable coincidence, because: 69 (decimal) = 105 (octal) 69 (hexadecimal) = 105 (...