Primality vs Eternal Clock
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Primality
This app determines if a given integer is prime or provides its prime factors. It also calculates the ordinal position of prime numbers found, up to a certain limit.
- Primality testing
- Prime factorization
- Prime ordinality calculation
- Large integer support (up to 999,999,999,999)
- Clean and simple interface
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The Primality App has a clean and simple, yet powerful, function: Given any integer, the app determines either that the given integer is prime or else it provides all prime factors of that integer. Very clean, very simple, focussed. The app operates in the range of 0 - 999,999,999,999. A popular feature of the app is its ability to determine the prime ordinality of each prime found, such as observing that 97 if the 25th prime. (However, this particular feature is available only up to the 100,000th prime, which is 1,299,709.) Requires iOS 13 or higher.
Eternal Clock
A minimalist digital clock that displays the time with no distractions. It offers a clean interface with subtle visual cues like a sun, moon, or mealtime hints, all without ads, data collection, or notifications.
- Ad-free experience
- No data collection
- No push notifications
- Minimalist interface
- Subtle visual cues (sun, moon, food)
- No settings or permissions required
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A pure digital clock. Nothing more, nothing less. It does one thing perfectly: shows the time. - No ads - No data collection - No push notifications - No permissions - Not even settings Sometimes a sun, sometimes a moon. At mealtimes, a playful hint of food. Still, nothing more than time — free from risks, interruptions, or hidden fees.
Screenshots
Verdict
The clearest difference is update cadence: Eternal Clock at weekly against Primality's every 2 months. Primality's advantage is ratings volume (24 vs 1). On price, rating, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 4.9 for Primality against 5.0 for Eternal Clock. That said, the two scores are not equally well evidenced: Primality has 24 ratings behind it against 1, so its average is the more settled of the two.
Primality ships an update every 2 months, Eternal Clock weekly. The most recent releases landed on October 13, 2026 and October 4, 2026 respectively.
| Parameter | Primality | Eternal Clock |
|---|---|---|
| Price | Free | Free |
| Rating | 4.9 (24 ratings) | 5.0 (1 ratings) — better |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 24 — better | 1 |
| Update frequency | Every 2 months | Weekly — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 13.2 | 12.0 — better |
| Further details — not scored | ||
| Size | 1 MB | 23 MB |
| Age rating | 4+ | 4+ |
| Developer | Bruce Schechter | Daehyeon Shin |
Customer experience
Primality
Eternal Clock
In-app purchases
Primality
No in-app purchases
Eternal Clock
No in-app purchases
Questions
Is Primality free?
Is Eternal Clock free?
Which has better reviews, Primality or Eternal Clock?
Do Primality or Eternal Clock have ads?
Which is updated more often, Primality or Eternal Clock?
Other comparisons
