RPNu vs isPrime?
Price, ratings, monetisation and update history for both apps, side by side β with what reviewers say about each.
RPNu
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RPNu is a calculator that makes crunching numbers easier than itβs algebraic equivalent. RPN stand for Reverse Polish Notation (The βuβ stands for universal, meaning it runs on both the iPad and iPhone.) and is the numeric evaluation method used for this app. RPN, I feel, is far superior to the algebraic method and once learned you will never want to use the algebraic again. This calculator has all the normal mathematical function, but also contains a host of other functions that you may find very useful. Space is limited in this description but here are the highlights: Help: There is extensive help to aid the user in determining how to use this app. It is also context sensitive. Programable: You can write your own programs and there are many tools to aid you in doing this. Graphics: You can graph equations and there are several modes to cover almost all requirements. A universal converter that you will find very useful. Matrix arithmetic (determinate, invert, add, subtract and multiply). Date calculator and an hours calculator with moon phase display. Elements and periodic table information. Combinations and permutations calculator Equation integration and root finder. Amortization with many useful functions. Mapping function that allows you to determine distance between points and other functions. Hyperbolic functions. Hexadecimal, Octal, and Binary modes. Barometer function showing QNE and QNH. A compass that not only shows magnetic and true north, but also shows the address you are at. This app includes extensive support for a Bluetooth keyboard. Also, extensive support is given to export your calculations to either email or the universal clipboard.
isPrime?
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It's a fast prime number checker.
Screenshots
Verdict
The clearest difference is update cadence: RPNu at every 2 months against isPrime?'s every 16 months. On price, ads, in-app purchases and device support there is nothing between them.
Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
RPNu ships an update every 2 months, isPrime? every 16 months. The most recent releases landed on October 26, 2026 and October 25, 2026 respectively.
| Parameter | RPNu | isPrime? |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 2 months β better | Every 16 months |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.0 | 15.0 |
| Further details β not scored | ||
| Size | 49 MB | 4 MB |
| Age rating | 4+ | 4+ |
| Developer | Scott Johnson | Omer Faruk Mesebuken |
In-app purchases
RPNu
No in-app purchases
isPrime?
No in-app purchases









