How to cite an article with an article number (instead of page range) I am curious to know what is the standard way (in AMS style) to cite a journal article that has an article number and/or a page range.
For instance, here is a BibTeX entry from MathSciNet of an article published in Proceedings A:
@article {MR4212412,
    AUTHOR = {Kallosh, Renata},
     TITLE = {M-theory, black holes and cosmology},
   JOURNAL = {Proc. A.},
  FJOURNAL = {Proceedings A},
    VOLUME = {477},
      YEAR = {2021},
    NUMBER = {2245},
     PAGES = {20200786, 15},
      ISSN = {1364-5021},
   MRCLASS = {83E30 (83C57 83E50)},
  MRNUMBER = {4212412},
       DOI = {10.1098/rspa.2020.0786},
       URL = {https://doi.org/10.1098/rspa.2020.0786}.
}

As you can see, the PAGES field contains both the article number 20200786 as well as the number of pages 15. On the other hand, it seems more logical to me to just write 1--15, because the article in question does have page numbers, and they run from 1 to 15. (The latter approach is in accordance with APA style; see here.)
In other cases, like articles published in Physical Review Letters (which is not covered by MathSciNet), an article has a six-digit number (e.g., 238104) and the $n$th page is identified by 238104-$n$.
How would you cite these articles? The AMS Style Guide completely ignores the issue.
EDIT. Since I posted the question, the format of the BibTeX entry of an article with an article number has changed in MathSciNet. The number itself is now preceded by the expression "Article no.". For instance, the PAGES field of the given Proceedings A article now reads as follows:
PAGES = {Paper No. 20200786, 15}

 A: I suggest to format this bibliographic reference as follows:
Renata Kallosh.
M-theory, black holes and cosmology.
Proceedings of the Royal Society A 20200786 (2021).
doi:10.1098/rspa.2020.0786,
arXiv:2009.11339.
Rationale: The purpose of a bibliographic reference is
to give the reader a very rough idea what the article is about and when it was written and to allow the reader locate the full text of the article as fast as possible.
The former purpose is achieved by including the title, author, and year.
The latter purpose is achieved through a multitude of ways.
If the article is accessed online, through a format like PDF or HTML,
then the DOI link at the end of the reference instantly takes the reader
to the referenced article.
If the article is printed on paper, and the reader wants to locate
the referenced article online, then my impression
is that by far the most common method is to supply a search engine with the last name and title of the paper.
This method almost always succeeds, but occasionally it is necessary
to include precise and unambiguous information,
especially if the journal is obscure and/or the article was published
a long time ago.
That's why the journal name and article number should be included, just in case.
I would suggest not to include the volume, issue, or page numbers,
since these are completely redundant in presence of an article number and including four different numbers makes it confusing which one should be used.
I would also not worry about potentially confusing this number with some other
information.
Whether we like it or not, this format will become increasingly more common, and soon everybody will be
aware that a number with more than 4 digits in a bibliographic
reference must be the article number.
I also recommend against abbreviating authors' names or journal names.
Not abbreviating authors' names makes it easier to search online
for a particular author.  This is especially important
for some very common last names, e.g., MathSciNet currently lists 20026 authors with the last name Wang.
Not abbreviating journal names makes easier to search for really obscure
journals.  (The interlibrary loan service at my university,
for example, requires unabbreviated journal names.)
Of course, a particular journal can (and often will) change
the format of bibliographic reference to suit its style.
However, many journals will preserve your DOI and arXiv hyperlinks if you include them.
Additionally, an important factor to keep in mind is that
if your paper is available on arXiv, more than 90% of downloads
of your paper will be from arXiv and not from the publisher's website.
(If you know a source with precise data, please indicate it in the comments.)
Accordingly, the overwhelming majority of the readers
will see the references the way the author formats them,
whereas the publisher's version will only be seen by a minority.
