Figure 211 Count, Numerical Count, and Sum will ignore text cells.
If one of the highlighted cells is an error such as #N/A, the Sum and Average statistics will not appear in the status bar.
Figure 212 An error cell will cause the Sum statistic to disappear.
Sometimes, when you are trying to find a lone #N/A within a column, it is fastest to start at the top of the column, hold down the Shift key, and start pressing PgDn. As soon as the Sum statistic disappears, you know that you have recently paged past the first #N/A error. (With 1 million rows, it might be faster to use Home, Find & Select, Go To Special, Errors.)