Calc is a free Java j2ME based Scientific, Statistical, Financial, Programmable, Graphing, Complex arithmetic, Matrix/vector arithmetic, RPN Calculator for any mobile phone that supports Java MIDP. And here’s an interesting fact:

Using the Real Java floating point library, Calc has 63 bits internal precision, which amounts to approximately 19 decimal digits accuracy, considerably more than normal calculators and computers. The exponent is 31 bits, which allows for numbers up to 4.197?10323228496

Direct download links-
http://midp-calc.sf.net/Calc.jad
http://midp-calc.sf.net/Calc.jar