It's About Prime 1.0
It's About Prime is capable of factoring numbers as large as 2^64 - 1 with the standard Macintosh Interface, using custom routines.
No other program can handle numbers over 2^32 - 1, which is only 4,294,967,295. And since the Mac "signs" the 32-bit numbers, technically, the largest number you can type into a dialog box is 2^31 - 1 or 2,147,483,647.
It's About Prime can show that 18,446,744,073,709,551,615 = 3 x 5 x 17 x 257 x 641 x 65,537 x 6,700,417 in less than one second. It can also show the hardest composite to factor less than 2^64 (18,446,744,073,709,551,597) = 3 x 6,148,914,691,236,517,199 after only two minutes of computation.
It's About Prime also verified the largest prime less than 2^64 is 2^64 - 59, or 18,446,744,073,709,551,557 for those of you who do not have a WideCalc program to display all of this fascinating information.