For most Android versions:
- Go to the "Settings" option for your device.
- Scroll down to the "Device" category.
- Find and click on the "Apps" listing.
- Find and click on the App icon/title.
Name of the App should be shown in the upper-left corner.
The Version Number should be shown immediately below the title.
- Additional information may also be shown here, including Permissions, Last Date updated, etc.
This information can be very beneficial, and often absolutely necessary when troubleshooting issues.
Note: This is also the screen you will go to if you need to "Clear Cache", "Clear Data", "Stop", or "Uninstall" the App.