# PFD Calc vs Prime Not Prime

The clearest difference is ads: Prime Not Prime at none against PFD Calc's shown. PFD Calc's advantage is device support (3 vs 1) and iOS requirement (15.0 vs 17.0). On price, update cadence and in-app purchases there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

PFD Calc ships an update every 5 weeks, Prime Not Prime monthly. The most recent releases landed on November 4, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | PFD Calc | Prime Not Prime |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.3 (6 ratings)](https://appshunter.io/ios/app/prime-not-prime/id6738664674/reviews)** |
| Number of ratings | — | **6** |
| Positive reviews | — | 100.0% of reviews |
| In-app purchases | No | No |
| Ads | Yes | **No** |
| Update frequency | Every 5 weeks | **Monthly** |
| Monetization | — | Free |
| Size | 14 MB | 15 MB |
| Requires iOS | **15.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Kazuhisa Kobayashi](https://appshunter.io/developer/1580882000) | [Richard Witherspoon](https://appshunter.io/developer/1690898003) |

## What reviewers say

### PFD Calc

[App page](https://appshunter.io/ios/app/pfd-calc-prime-factorization/id6737405828)

**Features:** macOS Compatibility

**In-app purchases:** none


### Prime Not Prime

[App page](https://appshunter.io/ios/app/prime-not-prime/id6738664674)

A fast-paced game that combines number recognition with a swiping mechanic. Players swipe right for prime numbers and left for non-primes, aiming to build long streaks. It's designed to be both educational and entertaining, with leaderboards for competitive play.

**Highlights:** Addictive swiping gameplay, Test prime number knowledge, Build streaks and complete challenges, Global leaderboards, Vibrant visuals and animations

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is PFD Calc free?

PFD Calc is free to download, with no in-app purchases.

### Is Prime Not Prime free?

Prime Not Prime is free to download, with no in-app purchases.

### Do PFD Calc or Prime Not Prime have ads?

PFD Calc shows ads; Prime Not Prime does not.

### Which is updated more often, PFD Calc or Prime Not Prime?

PFD Calc ships an update every 5 weeks, and Prime Not Prime monthly. Most recently, PFD Calc was updated on November 4, 2026 and Prime Not Prime on October 30, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*