product of all integers between 1 and the integral input of the function
FactorialReIm
In mathematics, the factorial of a non-negative integer ... {\displaystyle {\begin{aligned}n!&=n\times (n-1)\times (n-2)\times (n-3)\times \cdots \times 3\times 2\times 1\\&={\begin{cases}1,&{\text{if }}n=0\\n\times (n-1)!,&{\text{if }}n\geq 1.\end{cases}}\\\end{aligned}}} For example, ... ... … Wikipedia
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Wikipedia
en.wikipedia.org β€Ί wiki β€Ί Factorial
Factorial - Wikipedia
1 week ago - In mathematics, the factorial of a non-negative integer ... {\displaystyle {\begin{aligned}n!&=n\times (n-1)\times (n-2)\times (n-3)\times \cdots \times 3\times 2\times 1\\&={\begin{cases}1,&{\text{if }}n=0\\n\times (n-1)!,&{\text{if }}n\geq 1.\end{cases}}\\\end{aligned}}} For example, ... ...
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Statlect
statlect.com β€Ί glossary β€Ί factorial
Factorial | Use in probability and statistics
The factorial of a natural number is the product of all natural numbers smaller than or equal to . On this page we provide a basic introduction to factorials and we explain how they are used in probability theory and statistics.
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Purplemath
purplemath.com β€Ί modules β€Ί factorial.htm
What are factorials, and how do they work? | Purplemath
The factorial of a whole number n, denoted as n!, is the product of all the whole numbers between 1 and n: 1Γ—2Γ—3×…×(nβˆ’1)Γ—n. So 3! would be 1Γ—2Γ—3 = 6.
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Penn State Statistics
online.stat.psu.edu β€Ί statprogram β€Ί reviews β€Ί algebra β€Ί factorials
A.3 Factorials | STAT ONLINE
A factorial is a mathematical operation in which you multiply the given number by all of the positive whole numbers less than it. In other words \(n!=n \times (n-1) \times …
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Steemit
steemit.com β€Ί math β€Ί @gaultier β€Ί what-is-a-factorial-and-how-are-factorials-used-in-statistics
What Is A Factorial and How Are Factorials Used In Statistics? β€” Steemit
April 4, 2018 - The factorial of a number is the product of the integers from the number down to one. Factorials are used in probability, combinations, and permutations. The factorial function is one of the most important in statistics and probability. The function is written as n!
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ThoughtCo
thoughtco.com β€Ί factorial-in-math-and-statistics-3126584
What Is the Factorial (!) in Mathematics and Statistics?
May 14, 2025 - Courtney K. Taylor, Ph.D., is a professor of mathematics at Anderson University and the author of "An Introduction to Abstract Algebra." ... A factorial is multiplying a number by all whole numbers less than it down to one.
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IBM
ibm.com β€Ί support β€Ί pages β€Ί computing-factorial-n-spss-statistics
Computing the factorial n! in SPSS Statistics
Can SPSS Statistics compute factorials? That is, n! = n * (n-1) * (n-2) * ... * 3 * 2 * 1 Β· [{"Product":{"code":"SSLVMB","label":"IBM SPSS Statistics"},"Business Unit":{"code":"BU048","label":"IBM Software"},"Component":"Not Applicable","Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"Not Applicable","Edition":"","Line of Business":{"code":"LOB76","label":"Data Platform"}}]
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Cuemath
cuemath.com β€Ί numbers β€Ί factorial
Factorial - Meaning, Formula | Factorial of Hundred & 0
The Factorial of a whole number 'n' is defined as the product of that number with every whole number less than or equal to 'n' till 1. For example, the factorial of 4 is 4 Γ— 3 Γ— 2 Γ— 1, which is equal to 24. It is represented using the symbol '!' So, 24 is the value of 4!. The study of factorials ...
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Statistics How To
statisticshowto.com β€Ί home β€Ί factorial: simple definition, examples & distribution
Factorial: Simple Definition, Examples & Distribution - Statistics How To
June 11, 2024 - It’s a shorthand way of writing numbers. For example, instead of writing 479001600, you could write 12! instead (which is 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1). In algebra, you probably encountered ugly-looking factorials like (x – 10!)/(x + 9!).
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NCalculators
ncalculators.com β€Ί statistics β€Ί factorial-calculator.htm
Factorial of a Number (n!) Formula & Calculator
In mathematics, the product of all positive integers less than or equal to n (i.e) n! = n x (n-1) x (n-2) x .... x 1. The value of 0! = 1. The factorial function is extensively used in permutaions (nPr) & combinations (nCr), probability & statistics, calculus, algebra & other advanced mathematical analysis.
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Reddit
reddit.com β€Ί r/learnmath β€Ί what does factorial mean realistically ?
r/learnmath on Reddit: What does factorial mean realistically ?
June 12, 2020 -

Never bothered to understand maths ever, and am now reading cryptography as a hobby in spare time, so help me guys please.

I got that the factorial means just the product of numbers , eg : 4! = 4 Γ— 3 Γ— 2 Γ— 1

Lets say, take a letter for english alphabet and replace it with another random letter for eg :

A = I B = H

,then the books says the decryption keys will be equal to 26 factorial or 26! (since there are 26 letters in english alphabet)

This doesnt' make any sense whatsoever , if the question is too basic please point to another sub if possible. I googled the shit out of it and still don't get it.

Top answer
1 of 10
98
It is describing how many ways that a substitution key can be created. Walk through it this way. Assume that we start with A. What alphabet replaces 'A'. It could be anything from A to Z. So there are 26 choices of a substitute. OK. Let's for the purpose of this example say 'A's will be replaced by 'K'. Now go to B. What alphabet replaces B? Since we already assigned K to replace A, there are only 25 alphabets to choose from. By the time you get to Z, there will be only one unassigned substitute. So how many keys total? There are 26 choices from our starting point, then 25, then 24 all the way to 1. Therefore there are 26 * 25 * 24 *... * 1 ways of creating a unique key and this is called 26! from the definition of factorials.
2 of 10
7
What the book is saying is that "there are 26 factorial possible keys for a simple substitution". To see why this is true let's go through part of the process: What will A be changed into? Well there are 26 possibilities. We could say that A doesn't change or we could say it changes into any other letter. Let's pick L and say A -> L is one of our rules. Now, what will B get changed into? There are only 25 possibilities left if we want the cipher to work. B can get changed to any letter except L because we've already decided that A turns into L. If B became L then when decoding there would be no way to know if L meant A or B. So let's make the rule B -> K. For C there are only 24 possibilities, following the same logic. And so on down to Z which will have only one option.
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GeeksforGeeks
geeksforgeeks.org β€Ί mathematics β€Ί factorial
Factorial in Maths: Definition, Formulas & Applications - GeeksforGeeks
For a positive integer n: n! = n x (n-1) x (n - 2) x ..... x 1 Β· The factorial of a natural number n indicates the number of ways n items can be arranged.
Published Β  December 29, 2025
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TutorialsPoint
tutorialspoint.com β€Ί statistics β€Ί factorial.htm
Statistics - Factorial
Statistics - Factorial - Factorial is a function applied to natural numbers greater than zero. The symbol for the factorial function is an exclamation mark after a number, like this: 2!
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Physics Wallah
pw.live β€Ί curious-jr β€Ί exams β€Ί factorial
Factorial: Meaning, Formula, Values for Numbers 1 to 10
The factorial of a number 'N' represents the product of integers from 1 to N. Learn the steps to calculate factorial values from 1 to 10 and its use in statistics.
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Cuemath
cuemath.com β€Ί numbers β€Ί factorial-notation
Factorial Notation - Definition, Formula, Examples, FAQs
Factorial notation is represented as n!, and is equal to the product of all the positive natural numbers from 1 to n. n! = 1 x 2 x 3 x 4 .....xn. Factorial notation is extensively used in all the formulas of permutation and combination.
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Free
factorielle.free.fr β€Ί index_en.html
All about factorial notation n!
Factorials are also used extensively in probability theory. The numeric value of n! can be calculated by repeated multiplication if n is not too large. That is basically what pocket calculators do. The largest factorial that most calculators can handle is 69!, because 70!
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Reddit
reddit.com β€Ί r/explainlikeimfive β€Ί eli5: what is a factorial and how does it work
r/explainlikeimfive on Reddit: ELI5: What is a factorial and how does it work
December 31, 2024 - To elaborate on this a little, ... series, empty product, binomial coefficients and gamma function. ... For a natural number n, the factorial n!...
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Math is Fun
mathsisfun.com β€Ί numbers β€Ί factorial.html
Factorial Function !
The factorial function (symbol: !) says to multiply all whole numbers from our chosen number down to 1. Examples:
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Nicholas Lab
sites.nicholas.duke.edu β€Ί statsreview β€Ί math β€Ί factorial
Factorial! – ENV710 Statistics Review Website
May 22, 2018 - Factorials! Statisticians use factorials when calculating potential combination and permutations and using the binomial equation. A factorial, represented by an explanation mark (!), denote…
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Unacademy
unacademy.com β€Ί jee exam β€Ί jee study material β€Ί mathematics β€Ί factorial
Notes on FACTORIAL
March 29, 2022 - The factorial of 0 is 1, symbolically represented by 0! = 1. when n = 0, then n! is a product that involves the product of no numbers at all.