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Warning this app is only for nerds and math geeks! Do not expect any real value.

Prime Date & Time

You can calculate the next prime Times. A time is a prime time, if its digit representation, consisting of the year, month, day, hour and minute is a prime number. For example the April 24, 2016 at 8:23 pm is a prime time ( 2016 04 24 20 23 is prime )

Prime Factors

Decompose the current date or time into its prime factors. In the table you finde more information about the current date or time.


Check the Calendar for prime dates. Watch out for prime sundays (Primsonntag). Don't forget to give the mathematicians in your circle of friends a prime sunday present.

Ulam Spiral

The Ulam Spiral starts at the point you selected in the settings Section. Switch the presentaion of ulam spirals in the settings. More options, including the semi primes with a long press on the spiral.

Twin Primes: Pink : A prime number p is called a twin prime, if p+2 i also prime
Cousin Primes: Brown : A prime number p is called a cousin prime, if p+4 is also prime
Sexy Primes: Red : No explanation nessesary
Sophie Germain: Black : A prime number p is a Sophie Germain prime, if 2p+1 is also prime
All other primes are shown in blue.

Start the play mode at the toolbar and feel the primes ticking. There is also a fast mode in the toolbar, calculation 41 numbers per second. Or swipe through the numbers by swiping left or right on the spiral.


The graphical reprensentation of the prime factorization starts at the point you selected in the settings. Multiple Factors will shine brighter than others. Try it by setting the startnumber to 2 and switching the view mode to Number.

You can animate the pictures with the toolbar on the bottom. Or you can manually swipe through the numbers by swiping left or right.


There are different options for the definition of the primeness of a number. In the settings you can switch beetween the following possibilities:

Distance : The distance to the next prime number relative to the span from the previous prime to the next prime.
Number of Divisors : The presentaion shows the log of the number of divisors
Sum of Divisors : The presentation show the log of the sum of divisors. Minimal Values in red.
The Number of Columns depends on the selected View-Mode:

Date : The left top corner is Januar the first of the current year. Each row showing one Month.
Time : The left top corner represents midnight. Each row showing one hour with 60 minutes
Moment:The left top corner respresents the start of the current hour. Each row represneting one minute and each tick a second
Number: The start point deponds on the choosen number in the settings, and starts with the last digit of zero. Each column represents the last digit of the tested numbers
Prime Game
Find the factorization of a number. At least one of the Buttons on the bottom is a correct factor.

Notification: The app will notify you - even on your watch - about the next prime times. Do not get nervous, the spook will end after five prime moments.


Share your prime moments via Mail, Facebook or Twitter #primetimer. Use the Share button in the Navigation Bar


Look at the top of the Info Screen: Which color have the numbers. If you see primes in red, maybe you have to check for the savant syndrom. What color have the twin primes? Can you feel the prime numbers?

Watch Support

Select the complication of your choice to stay informed about the next prime times.

With a deep press on the prime watch, you can change the mode of the presentation

32-bit iPhones prior to Version 5s: Due to limited calculating power you will have to wait up to ten seconds at the first start of the app. A 64-bit iPhone (5s, 6, 6s, 6+, 6s+, 5se) is recommended.
Stephan Jancar