When you state that you 'deleted' those apps, do you indeed mean you intentionally when into the Settings >> Apps menu and Uninstalled those apps? Or is it just a matter where you deleted the icons for those apps off the screen?
Things like a Calculator app are typically included as default apps so they're an integral part of the installed Android operating system on your phone. In order to actually delete a pre-installed, system-level app, you need to go through the process of rooting your phone. Otherwise, being just a typical user, like most of us, you don't have the required permissions status to do things like delete protected apps and things.
If all did was inadvertently delete the screen icons, the actual apps are still on your phone. It's just now those icons are gone. If you swipe upwards from the bottom of a screen that should bring up the apps menu, and you can find what apps you want and then drag-and-drop the icon onto the screen.
Another option is to look for alternatives in the Play Store, most third-party app options will be just as or better than the default apps -- i.e. there are a number of other Calculator apps available that have a really extensive feature set and some with more ways the customize the user interface.