The most common word for a number that is not rounded up or down, nor approximated in any way is "exact".
The fact that the number is without a decimal and expressed to nine significant figures should be enough for most people to realize it is the exact number, but you can indicate it specifically if you like.
This is an archaic use of the subjunctive. It may have been somewhat archaic even 200 years ago. It means
to tell it would be no easy task.
If he had written
to tell it was no easy task,
it would mean that he had already told it (which he hasn't; he's explaining it's savage and wild beyond his powers of description).
And if he had written
To me 'is' sounds right, but I'm wrong, according to Oxford dictionaries:
Although the expression ‘a number’ is strictly singular, the phrase ‘a number of’' is used with plural nouns (as what grammarians call a determiner (or determiner)). The verb should therefore be plural:
If you notice that each other, while idiomatic, is not unbreakable, it begins to come clear.
The reciprocal phrase each other can be separated into one determiner binding something in the subject (each, each one), and one determiner binding something in the object (other, the other), viz:
Each (one) of us knows what the other (one (of us)) is doing. (dual)
I think 'eye movement changes' is fine as part of a descriptive title. In that case, 'eye movement' acts as a compound adjective to modify the noun 'changes'.
I have found at least one other paper in a respected journal that uses this, the full title of which is:
Saccadic eye movement changes in Parkinson's disease dementia and dementia with Lewy bodies
When referring to multiple individuals or groups, you usually (check answer linked in Edwin Ashworth's comment down below) go with the plural form of the noun that is common to all the individuals or groups. Thus, "noses" would be grammatically correct.
Ibrahim, and welcome to ELU.
First of all, you are right in your distinction between nouns that have no plural (like information) and nouns that have a plural (like reference). Strictly, nouns without a plural are called count nouns. It is not the nouns that can or cannot be counted, but the things to which they refer.
Some nouns can be used as either ...
You can't possibly have counted the bees to find their exact number, and this exact number is irrelevant anyway. Your comment is more that the amount of bees is unusually high. So "number" is, as BillJ says, a non-count quantification noun. So you are referring to the bees collectively, so "There are an unusual number of bees".
Compare "Eleven is an unusual ...
There is/are an unusual number of bees this summer.
"Number" is a non-count quantification noun here, which is said to be 'number-transparent' for verb agreement purposes. This means that it is the number of the noun that is complement of the preposition "of" (called the 'oblique') that determines the number of the whole NP.
As it happens, in its number-...
As to the general question you ask, yes, plural nouns can be followed immediately by another plural noun. Here is an example: "I gave each of my cousins presents."
However, your example "notifications settings" suggests you are really interested only in compound nouns, since that's what "notification setting" is. The main stress in this example is on "...
In English, generically engaging in an activity can be given in the singular form.
play a musical instrument
ride a bike
mow a lawn
cook a meal
drive a car
crank out an article [write an article]
take a taxi
make a profit
It can be argued that all the examples above link the verb to the item to express engaging in an activity. The nouns are "intimately" ...