I can't find this row in php.ini, so is there any way to do that?
So ok, I understood, the answer is not, then how should I calculate the result of this task if I want it do with php?
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
You can increase PHP_INT_MAX. As others have said, PHP_INT_MAX is platform dependent. That means on 32 bit hardware or a 32 bit OS or a 32 bit compile of PHP, PHP stores the bit in 4 bytes (max of about 2 billion). However, if all 3 are 64 bit, the max goes to 8 bytes (about 9e18 or 9,000,000,000,000,000,000).
So if you really want large ints, get a 64bit machine, and a 64bit OS, and a 64bit compile of PHP...
You can not control it actually. However, if you are dealing with BIG numbers, I would suggest you the:
BC Math extension.
No.
From http://www.php.net/manual/en/reserved.constants.php:
These constants are defined by the PHP core. This includes PHP, the Zend engine, and SAPI modules.
Nope. It's hardware/os limitation, not PHP.
You can use bcmath fructions for large numbers