PrimeXTime vs Serial 7s
Price, ratings, monetisation and update history for both games, side by side — with what reviewers say about each.
PrimeXTime
Engage your mind with a unique number-based puzzle game. Start with a random number and strategically divide by single-digit primes. Bump the number by multiplying by 10 and adding a digit to reach 1 and win.
- Number division by primes
- Strategic bumping mechanic
- Goal to reduce number to 1
- Brain exercise gameplay
- Simple, intuitive interface
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Kill some time and give your brain a little exercise at the same time with this simple game. You start with a random number and then start dividing by single-digit primes (2, 3, 5 or 7). When you can't do any more divisions you 'bump' the number -- multiplying by 10 and adding any single digit. You win the game by reducing the original number to 1.
Serial 7s
This game challenges you to rapidly subtract 7 from a starting number until you can no longer continue. It's based on a cognitive test used to assess attention and memory, with consistent play potentially improving brain skills and helping to prevent cognitive decline.
- Serial 7 subtraction gameplay
- Tests attention and memory
- Helps prevent cognitive decline
- Measures subtraction speed
- Randomized starting numbers
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Serial 7s is a brain training game that tests how fast you can perform continuous subtraction of 7 from a starting number. Inspired by the classic "Serial 7s" task—a standard component of the Mini-Mental State Examination (MMSE)—this game gives a proven cognitive test a fresh twist. Starting with a randomly generated number between 99 and 105, your total time to complete 14 consecutive subtractions of 7 is measured. Serial subtraction by 7 is widely used to evaluate focus, attention span, and working memory. Regular practice can help sharpen your mind and boost cognitive fitness. Recommended for anyone interested in brain training, keeping their mind active, or supporting long-term cognitive health and dementia prevention.
Screenshots
Verdict
The clearest difference is ads: PrimeXTime at none against Serial 7s's shown. PrimeXTime also leads on monetization model (free vs ad-supported). Serial 7s's advantage is iOS requirement (15.0 vs 17.6). On price, rating, ratings volume and update cadence 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 — 5.0 for PrimeXTime against 5.0 for Serial 7s. Both are backed by a comparable volume of ratings — 2 and 1 respectively.
PrimeXTime ships an update every 4 months, Serial 7s every 5 months. The most recent releases landed on September 28, 2026 and October 3, 2026 respectively.
| Parameter | PrimeXTime | Serial 7s |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (2 ratings) | 5.0 (1 ratings) |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 2 — better | 1 |
| Update frequency | Every 4 months — better | Every 5 months |
| Ads | No — better | Yes |
| In-app purchases | No | No |
| Monetization | Free — better | Ad-supported |
| Devices | iPhone, iPad | iPhone, iPad, iPod — better |
| Requires iOS | 17.6 | 15.0 — better |
| Further details — not scored | ||
| Size | 6 MB | 42 MB |
| Age rating | 4+ | 9+ |
| Developer | Rick Hutchinson | HFX Lab |
Customer experience
PrimeXTime
Serial 7s
In-app purchases
PrimeXTime
No in-app purchases
Serial 7s
No in-app purchases
