# Prime Factorization vs Stopwatch Library

The clearest difference is in-app purchases: Prime Factorization at none against Stopwatch Library's 1. Prime Factorization also leads on iOS requirement (8.0 vs 17.0). Stopwatch Library's advantage is update cadence (every 3 days vs every 3 months). On price, ads and device support there is nothing between them.

Both are free to download. Stopwatch Library sells 1 one-off in-app purchase. Prime Factorization asks for nothing beyond the download.

Prime Factorization ships an update every 3 months, Stopwatch Library every 3 days. The most recent releases landed on September 30, 2026 and September 28, 2026 respectively.

## The numbers

| Metric | Prime Factorization | Stopwatch Library |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.4 (5 ratings)](https://appshunter.io/ios/app/prime-factorization/id528980227/reviews)** | — |
| Number of ratings | **5** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 3 days** |
| Monetization | Free | — |
| Size | 2 MB | 5 MB |
| Requires iOS | **8.0** | 17.0 |
| Devices | iPhone, iPod | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Sohei Mori](https://appshunter.io/developer/528980270) | [Naoyuki Hasegawa](https://appshunter.io/developer/6777422704) |

## What reviewers say

### Prime Factorization

[App page](https://appshunter.io/ios/app/prime-factorization/id528980227)

This utility app breaks down integers into their prime factors. It also calculates the number and sum of divisors, lists all divisors, and identifies specific number types like prime, perfect, abundant, or deficient.

**Highlights:** Prime factorization of integers, Calculate number of divisors, Sum of divisors calculation, List all divisors, Identify prime numbers, Identify perfect, abundant, deficient numbers

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

**In-app purchases:** none


### Stopwatch Library

[App page](https://appshunter.io/ios/app/stopwatch-library/id6794338987)

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 広告を削除 | $2.99 | one-time |


## Frequently asked questions

### Is Prime Factorization free?

Prime Factorization is free to download, with no in-app purchases.

### Is Stopwatch Library free?

Stopwatch Library is free to download, with in-app purchases available.

### Do Prime Factorization or Stopwatch Library have ads?

Neither Prime Factorization nor Stopwatch Library shows ads.

### Which is updated more often, Prime Factorization or Stopwatch Library?

Prime Factorization ships an update every 3 months, and Stopwatch Library every 3 days. Most recently, Prime Factorization was updated on September 30, 2026 and Stopwatch Library on September 28, 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.*