The description of Prime Finder
Prime Finder lets you find primes of all sizes, and primes that follow formulas and simple digit patterns.
This App has 6 main options:
1) test any number to see if it is prime;
2) find primes with any number of digits;
3) find primes near any number;
4) find primes that follow a digit pattern like
11, 111, 1111, 11111, or 7, 97, 997, 9997 ... etc.;
5) find primes that follow a formula, like
n^2 + 1 for n = 1, 2, ... .
6) make several expressions be prime simultaneously,
like n and n + 2 (twin primes).
These options can handle numbers up to 10,000 digits.
This App also contains data on the first 100 million primes. This App can:
7) find the nth prime (n can be as large as 100 million);
8) count the number of primes up to x (x can be as large as 2,038,074,743).
1) this App uses the fast BPSW primality test to check whether a number is prime;
if it is not prime and has 30 or fewer digits, this App will factor it into primes;
2) you can copy the output to the device's clipboard;
3) it's free, has no ads, no special permissions are requested;
4) you can cancel a long calculation at any time;
5) built-in Help text has information about primes and prime testing,
along with links to more detailed Wikipedia articles.
If you find a bug, email me and I'll get to work on fixing it.
If you have a suggestion for a new feature, email me and I'll consider adding it.
This App has been tested on a Galaxy Tab, and Galaxy ii, 3, and 4 devices.