As far as I know there is no native function for this but here's something you can try.
Put these UDFs into a standard module.
Public Function SheetCount() As String
SheetCount = "There are " & ThisWorkbook.Sheets.Count & " sheets in this workbook."
Public Function FileSize() As String
FileSize = "The file size of this workbook is " & FileLen(ActiveWorkbook.FullName) / 1024 & " KBytes."
Then - after making sure you have saved the workbook - (ie, given it a name),
you can use these functions like so:
In one cell: =SheetCount()
And in another: =FileSize()