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.)