RPN Scientific

RPN Scientific is a scientific Reverse Polish Notation (RPN) calculator based on the venerable Hewlett Packard 10C scientific calculator. It is free, does not contain any ads, and does not collect any information about you or your device. It performs most of the 10C’s math functions but does not include the ability to be programmed. Users are assumed to be familiar with using RPN calculators. 
Results text can be copied to the clipboard. It also supports pasting of numbers from other applications.
RPN Scientific has a 25-level stack and supports ten store and recall memory locations. Values are stored between sessions. It supports fixed, scientific, general, engineering, and currency formats. The number of decimal places and/or significant figures displayed is set by the user in a popup window accessed via the menu icon on the upper left.
The calculator has a “tape” that records each calculation. If the display is too narrow (iPhone), the tape is not visible, but can be seen in a popup window selected with the menu icon. The tape can be copied and cleared; the tape font size can be adjusted.
The app responds to touch, mouse, and keyboard inputs. Key codes are generally intuitive. They are listed on the “About” page, which is accessed by using the menu icon.