Is "A number of..." plural or singular?

Is the following sentence correct?

A number of researchers are expected to attend the conference

Notice that the sentence is using the plural verb "are" after "researchers" but I don't know if it needs the singular verb "is" instead, since it says "A number" before "researchers".

Answer

Idiomatically, the expression a number of works the same way as words and phrases like many, several, quite a few, or plenty of. Therefore, it's:

• Many researchers are expected to attend.


• Several researchers are expected to attend.


• Quite a few researchers are expected to attend.


• Plenty of researchers are expected to attend.



• A number of researchers are expected to attend.