Number words - an exception

One strange exception to the rule given at Number words is the word number itself. We say "A number of points have been made", not "has been made", and "A number of people were present", not "was" - although the Subject of the verb is singular - "a number" - in both cases. Another exception that feels perfectly idiomatic to a native is "The staff were also responsible for ... " where a logical user of the language might prefer "The staff was responsible".

Numeral words like million and hundred are followed by a singular in modern English. Say three million or five hundred, even if you think - rightly - that logically it should be three millions and five hundreds. Human language is often not logical. (In older English, you will sometimes see these words used in their plural forms.)