Factor Expert

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My goals were to write a fast factoring App, and to provide some information about how to do factoring and primality testing.

Features:

1) this App one of the fastest factoring Apps that I know of;

2) it factors all numbers up to 36 digits, as well as some larger numbers;

3) you can enter your number as a mathematical expression;

4) you can copy the output to the device's clipboard;

5) it's free, has no ads, no special permissions are requested;

6) built-in Help text has lots more info about prime testing and factoring.

Most factoring Apps handle numbers up to only about 18 digits, and take nearly a minute to do so.

On average, this App factors 20-digit numbers in under 1 second, 30-digit numbers in under 12 seconds, and 36-digit numbers in under 7 minutes. (Some take more time, some take less).

You can enter your number by typing its digits.

You can also enter your number as an expression. This is helpful for entering large numbers. The screenshots illustrate this feature. The symbols are accessed via the "Sym" key on the standard keyboard.

When the factoring is done, you can save the output to the device's clipboard. You can then paste the output into other documents, email the results, etc.

This App first applies the very fast BPSW primality test to find out if your number is prime. If it is not prime, the App does most of its factoring using an advanced method called SQUFOF. This is much faster than dividing by every odd number up to the square root. The SQUFOF code is based on code kindly provided by Professor Samuel S. Wagstaff, Jr.

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.