There currently isn't a way to do this directly in our Analytics page. You can easily and quickly view the total number of subscribers through our REPORTS page. See this article HERE on how to do that.
We do have plans on adding additional reports you can run but for right now, this would be what you need to do in order to pull up that information.
1. Go to ANALYTICS - then LOGS
2. Change the Report filter to be "SMS inbox (Single)"
3. Make sure "All Numbers" is selected under User / Number
4. Add the date range you want to filter by
5. Click "Show"
6. Export and a .csv file should download
7. Open the document
8. Highlight the entire top row that lists the column's categories
9. Click the filter icon to add a filter to the row.
10. Click the drop down menu next to "TEXT MESSAGE" and select "Ascending"
11. Now the messages should be grouped together - this makes it easy to view how many people texted the keyword within that time period. You can even copy and past each keyword section to view it in its own spreadsheet.
Again, this is the current workaround but we do have plans to improve the reports and analytics.