# Prefacto - Prime Numbers — Check. List. Factor. Offline.

> Offline prime number calculator and generator with factorization and speed test. (iPhone/iPad app by Daniel Springer.)

- Source: https://appshunter.io/ios/app/prefacto-prime-numbers/id1402417667 (this page in markdown: same URL + `.md`)
- Developer: [Daniel Springer](https://appshunter.io/developer/1402417666)
- Category: Reference, Utilities
- Price: $4.99
- Rating: 4.70/5 from 19 App Store ratings · 7 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.0 · 1 MB
- Languages: American English
- Released: 2018-08-01
- Data updated: 2026-08-22
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/prefacto-prime-numbers/id1402417667/reviews.md

## What is Prefacto?

Discover the power of prime numbers with Prefacto!

Prefacto is your go-to app for everything related to prime numbers. Whether you're a math enthusiast, a student, or just curious, this app provides a comprehensive set of tools—all without requiring an internet connection.

FEATURES:

- PRIME NUMBER VERIFICATION: Instantly check if any number is prime.
- PRIME RANGE LISTING: Generate a list of prime numbers within any specified range.
- PRIME FACTORIZATION: Break down any number into its prime factors quickly and efficiently.
- GENERATE CUSTOM RANDOM PRIME NUMBERS: Create random prime numbers with customizable digits, up to 20 digits.
- SPEED TEST: Find out which phone is the fastest between your friends by racing up to 100 million.
- SAVE & SHARE RESULTS: Easily save or share your findings with others.

WHY PREFACTO?

- OFFLINE FUNCTIONALITY: Enjoy full functionality without needing an internet connection.
- LIGHTWEIGHT: Designed to be efficient and avoid taking up significant storage space on your device.
- SPEED: Experience fast calculations and instant results.
- MAXIMUM POWER: Check the **highest** numbers of **any** other app, thanks to advanced algorithms.

Dive into the fascinating world of prime numbers with Prefacto. Download now and start exploring!

## Key features

- Prime number verification
- Prime range listing
- Prime factorization
- Generate custom random primes
- Speed test
- Save and share results
- Offline functionality

## Recent user reviews (7 of 7)

All indexed reviews: https://appshunter.io/ios/app/prefacto-prime-numbers/id1402417667/reviews.md

### 5/5 — Well polished

*2024-08-08*

A powerful, fast, prime numbers galore app

### 5/5 — Glamorous!

*2024-03-31*

To be honest, I have never seen an app to this extent user friendly! It is extremely useful with simple design. That is what makes it so special to use!

**Developer response:** Thank you so much Ahz, that really means a lot!

-Dani

### 5/5 — 👍🏻 Is that number prime? There’s an app for that!

*2023-01-06*

Throughout the day, I’ll occasionally find myself wondering, “Is that number prime? If not, what are its factors? How far is it from other nearby primes?” If that sounds like you, then look no further – this is the app for you!

**Developer response:** Glad to hear you enjoy my little app, GB13, thank you!

### 5/5 — Prime app

*2022-07-24*

This is the PRIMEir app for prime numbers and is very fun. It's cool to look to see who's birthdays are on prime dates or not. Overall one of if not the best niche apps ever.👍👍👍👍👍

**Developer response:** Why thank you, Sebastian! Glad you like our little app

### 5/5 — An indescribable pleasure

*2021-12-22*

I’m not sure exactly why being able to calculate primes on the go is necessary; but somehow it’s empowering.  It scratches the same itch as the star tracking app.  Thanks guys.  Really love it.

**Developer response:** Thank you! Glad you enjoy my little app

### 5/5 — Awesome app!

*2021-12-02*

This is the app you were looking for. Clean, intuitive, precise. When you need a quick answer, google is too slow. Prime will give you all the info you need.

**Developer response:** Thank you for your delightful review! Please let us know if anything can be improved further. Thanks

### 5/5 — It’s useful

*2021-12-01*

Prime is an incredible app if like me, you are interested in some really cool math games. You can choose any game to start up with and go through each one of them and explore all the amazing info and tricks the app provides. Its also really useful because if you need to find out not only if a number is prime, but also by what you could divide it by, the app will do just that in a clear and fun way! It totally think YOU should get the app because its useful, fun, and overall an app that will make you feel smart😉

**Developer response:** Glad you find our little app useful! Thanks

## Frequently asked questions about Prefacto

### What is Prefacto?

Prefacto is a reference application designed for exploring prime numbers. It offers tools for verification, listing, and factorization of primes, all available offline.

### Does Prefacto work offline?

Yes, Prefacto is designed for offline functionality, meaning you can use all its features without an internet connection.

### How much does Prefacto cost?

Prefacto is a paid application, available for $4.99.

### What is the age rating for Prefacto?

Prefacto has an age rating of 4+, making it suitable for a wide range of users.

### What devices does Prefacto support?

Prefacto is available for iPhone, iPad, and iPod devices.

### How often is Prefacto updated?

The latest version is 8.22, and the app was last updated on January 8, 2026. This indicates a history of regular updates.

### Can I generate large prime numbers with Prefacto?

Yes, Prefacto allows you to generate random prime numbers with customizable digits, up to 20 digits in length.

### Does Prefacto have ads?

No, Prefacto is ad-free, providing an uninterrupted user experience.

## Version history (last 5 releases)

### 8.22 — 2026-01-08

Minor improvements

### 8.21 — 2025-10-10

Minor improvements

### 8.20 — 2025-07-30

Accessibility improvements

### 8.19 — 2025-07-27

Speed test your phone with your friends, now up to 100 million.

### 8.18 — 2025-07-24

You can now customize the app icon to be light, dark, or tinted (the app will automatically following your iOS settings)

This update includes lots of bug fixes and performance enhancements. If you ever want to abort a long operation, simply quit the app — and relaunch it to continue using it.

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## More apps by Daniel Springer

- [Mathee - Math Tricks & Games](https://appshunter.io/ios/app/mathee-math-tricks-and-games/id1406084758)
- [PickerFull - Color Extractor](https://appshunter.io/ios/app/pickerfull-color-extractor/id1410565176)
- [Motivator - Money Counter](https://appshunter.io/ios/app/motivator-money-counter/id6444535220)
- [MultiBuddy](https://appshunter.io/ios/app/multibuddy/id6449202900)

All apps by Daniel Springer: https://appshunter.io/developer/1402417666

## Related topics

[prime numbers](https://appshunter.io/ios/topics/prime-numbers)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-22.*