Tablets aren't typically great at data entry, as you have to hunt and peck for the numbers on the virtual keyboard.
Microsoft is trying to ease the pain, releasing its own Keyboard for Excel to the Play Store. It includes the traditional 10-digit keypad that still graces the right side of hardware keyboards, something number crunchers swear by for rapid data entry.
It only works in landscape mode, as it would put too tight of a squeeze on the rest of the keyboard on a vertical orientation. Because it's designed for this single purpose the keyboard doesn't have many other features like autocorrect or gesture typing, so don't count on it as a full-blown keyboard replacement. Also, because Excel is built only for tablets, those are the only devices on which you can install it.
The keyboard still works for entering text and symbols, so it should handle all your needs when using it with Microsoft Excel for Android.
Why this matters: Microsoft's strategy is to get you using Office, no matter the device. Office for Android puts the big three on your tablet: Word, Excel, and PowerPoint. This Excel-focused keyboard is a solid add-on for those who want to dabble with spreadsheet entry.