The site operator is not the reliable tool it once was, we have seen many here commenting on peculiar results. One thing to keep in mind is that Google views all those URL variations as being different sites. For this reason they expect webmasters to create a GSC account for each variation in order to ensure that you can see how they see each 'site'. You should be able to see the number of pages indexed in your GSC account.

Some of these suggestions may or may not apply to your case, but they are relevant and are things to check for when you have issues about indexing:

There may be people who visited your site and shared it on another site, using the wrong parameters or protocols. Google will try to visit those incorrect URLs and may even index them.

Technically, you are not required to submit a sitemap, but in some cases it can help Google understand how you want your properties indexed. When you change a site from http: to https: for example, you should only list https: URLs in the sitemap and they should not find old versions of sitemaps submitted. This also relates to canonical URLs to avoid content being viewed as duplicate.

If you have migrated your site at any time (from http: to https:, or from www to non www for example) ensure that it is done properly and that you see 301 responses (not 302) in your logs. Ensure that every old URL is landing on its new URL with a 301 server response. View your access logs to be certain of what Google is crawling.

Ohkay! So, the only way to know the actual no. of pages indexed by google is from GSC only!

Here's the correct syntax to use for the site operator command.

[support.google.com...]

Depending upon the site setup, you may get different results between example.com and www.example.com

Note, do not put a space after ":"

Either way, it's not accurate.

The best way to find out is to use GSC, assuming you are the site owner, of course.

What you will find with the GSC results listed above is---what is listed in GSC.

To know what pages g has indexed on your site just review your raw logs. Having said that, you will still not know what the g SERPS have, or how they will be presented due to all the issues not2easy listed above, and the fact that g's indexing is updated between their servers at different times and different days: CONSTANTLY.

Thanks @engine and @tangor.