Nothing but Primes
No winning. No ending.
Free · Designed for iPad. Not verified for macOS.
Numbers sink through deep water.
As they sink, they come apart into their prime factors.
12 becomes 2 and 2 and 3.
The primes drift to a number line at the edge of the screen, light up, and pass on.
Some numbers do not come apart.
Divisible only by 1 and themselves — primes.
Those stop where they are and glow amber.
- You do nothing
No arithmetic. Tapping does not make anything go faster.
There is no winning and no ending.
Touch the screen once to begin, and then watch.
- The number line is walked, not sampled
Numbers are not thrown out at random. They are taken in order, one at a time, from 2.
So twin primes — two apart — and prime deserts, long stretches with none at all,
appear exactly as they really are. Nothing here is staged.
- Amber means prime
That colour is used nowhere else in the app.
You do not have to learn which numbers are prime. The glowing ones are.
- A codex
When a number with some property drifts past, a card is added.
Taxicab 1729, perfect numbers, amicable numbers, Mersenne primes, prime deserts,
the sieve of Eratosthenes, semiprimes and RSA — twenty in all.
Every prime you have passed, and the whole number line you have walked, stay readable.
- You can slow it down
You can make it faster, and you can always put the speed back to how it began.
Nothing you have built up is lost by doing so.
- It stops, eventually
When the numbers grow too large, the app stops.
Either it reaches the edge of what a 64-bit integer can hold, or it meets a number
it cannot factor within the work allowed.
Calling something prime when it is not known to be prime is not an option, so it stops
and tells you why. That place is the foot of the wall the internet's encryption stands on:
instant to multiply, forbidding to take apart.
Everything is computed on your device. The network is used only to show ads.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
After you close the codex, the app may ask — once — for a review.
It only asks after you have gathered some cards, and it does not
interrupt the watching.
Small adjustments besides.
The developer, Koki Tanisaka, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Used to Track You
The following data may be used to track you across apps and websites owned by other companies:
- Location
- Identifiers
- Usage Data
- Other Data
Data Linked to You
The following data may be collected and linked to your identity:
- Identifiers
- Usage Data
- Diagnostics
- Other Data
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Location
- Identifiers
- Usage Data
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Koki Tanisaka
- Size
- 70.4 MB
- Category
- Entertainment
- Compatibility
Requires iOS 15.0 or later.
- iPhone
Requires iOS 15.0 or later. - iPad
Requires iPadOS 15.0 or later. - iPod touch
Requires iOS 15.0 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English and Japanese
- Age Rating
13+
- 13+
- Contains
Advertising
- Copyright
- © 2026 Koki Tanisaka