obj of prep (sing or plural)

[aziacks]

Hi everyone,

I need your help on a subject that I came stumbling on.

I don't know the rule or rules for whether the object of the prep should be plural or singular.

Example: Los Angeles has received numbers of immigrants in recent years.
Is it ok if numbers and immigrants be singular? If not why?
Example 2: I think the most wasted of all days is...bla bla bla.
Should it be day instead of days.

Is there a rule that tell whether I should label singular or plural after:
OF
ex: all the time(s)?
ex: all of the time(s)?
ex: of all day(s)?
ex: most of American(s)?

Thank you ahead.

[Tdol]

Los Angeles has received numbers of immigrants in recent years.
Los Angeles has received a number of immigrants in recent years.
Los Angeles has received a number of immigrant in recent years.

Simply, 'immigrants' has to be in the plural because more than one came. You could use it as compund, in which case it would not take the plural:
Immigrant numbers...

Time- this would be plural when in meant 'on every occasion/'- All the times I met him,
Most (of the) Americans- always plural.