Downloading APCalculator 20150111 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available.
Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. The application lies within Theming Tools, more precisely Multiple Desktops. This free Mac app is a product of K Crossen.
From the developer:
Though APCalculator (Arbitrary Precision Calculator) is initially set to 64 decimal digits internal precision, with 32 decimal digits displayed, this calculator can be set to any desired precision. Initial operating mode is RPN, which approximates the user interface of the HP-48/49 series calculators. Numeric display, even while entering numbers, features standard digit grouping.
You may want to check out more Mac applications, such as SplashId BlackBerry Desktop, Magic Menu or Trakkboard, which might be similar to APCalculator.