Somewhere in the past few hours, the millionth question was asked on Math.SE. Could someone cleverer than I am please figure out which one it was. Presumably there should be a plaque or statue, or somesuch commemoration. What would be suitable recognition for the questioner and the answer(s), if any? It will be interesting to see if it's a "good" question.

Any reasonable definition of "millionth question" would have been fine with me. But, to placate the folks who feel that this question is "opinion-based", let me suggest a definition: the millionth question is the one that caused the counter at the top of the main question page to reach 1,000,000 for the first time. By this definition, it was apparently Firat Celebi's "Separation Properties in Topology" question.

I have always felt that inventing suitable definitions is an important part of mathematics. It surprises me that so many people are critical of any question that requires such an invention.

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    $\begingroup$ The question was: Separation Properties in Topology $\endgroup$
    – user486983
    Commented Oct 8, 2018 at 3:08
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    $\begingroup$ It might be considerably difficult to pinpoint the one that was the millionth one at the time it was posted because the system runs a daily check to clean up abandoned questions, so that specific question is likely to appear not to be the millionth one now. $\endgroup$ Commented Oct 8, 2018 at 3:23
  • $\begingroup$ Screenshot by other user, justify this is 1,000,000 question. And it's about Topology.. $\endgroup$
    – user486983
    Commented Oct 8, 2018 at 3:28
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    $\begingroup$ Can you identify the 8th billionth person to live on earth? Since every second it could be that two or more babies are born, and two or more people die. How can you identify something so fluid? Does it really matter? $\endgroup$
    – Asaf Karagila Mod
    Commented Oct 8, 2018 at 7:04
  • $\begingroup$ @Isabella You probably mean the screenshot from this answer, right? $\endgroup$ Commented Oct 8, 2018 at 7:59
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    $\begingroup$ @AsafKaragila > Can you identify the 8th billionth person ... ". No, of course not. But that's a much more difficult question than the one I asked (as you probably know). Does it really matter? No, it doesn't matter at all; it's just interesting and fun, in my view. Like a lot of mathematics. $\endgroup$
    – bubba
    Commented Oct 8, 2018 at 8:47
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    $\begingroup$ Much more, yes. But the difficulties are the same. We have questions being deleted all the time, and new ones coming in all the time, and old ones getting undeleted all the time. We can say that definitively passed the millionth questions displayed, yes. But which one was the one? That's extremely hard to analyze. If I now go back and undelete a bunch of stuff from 2010, the answer will be different. If tomorrow the millionth question is deleted, the answer is again different. So... what's the point? $\endgroup$
    – Asaf Karagila Mod
    Commented Oct 8, 2018 at 8:58
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    $\begingroup$ @AsafKaragila Totally agreed about the pointlessness, but human beings don't come with a time-stamp precise to the second. :-) $\endgroup$ Commented Oct 9, 2018 at 0:49
  • $\begingroup$ @MartinSleziak I guess yes.. :) $\endgroup$
    – user486983
    Commented Oct 9, 2018 at 3:15
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    $\begingroup$ It does not matter which question was the one millionth, just that some question will always be the one-millionth now : we have more than one million questions, and are a very$^{6}$ exclusive site on the WWW now. Drink(juice) to the health of MSE! $\endgroup$ Commented Oct 9, 2018 at 6:30
  • $\begingroup$ Sorry, I have posted a wrong link in my previous comment. I meant this answer which contains this screenshot. $\endgroup$ Commented Oct 9, 2018 at 7:48
  • $\begingroup$ I bet you someone will come along now and delete half a million of them. $\endgroup$ Commented Oct 9, 2018 at 20:37
  • $\begingroup$ As eveidence to the fluid nature of the notion of 1000000th question: I though that a different question was it (cdf. math.stackexchange.com/questions/2946019/… ) and that was by counting backwards by just a few questions when the question counter showed just a bit more than 1000000 (IIRC, it was less than 1000020). Apparently, already in that short timespan, some deletions or other effects caused deviation. $\endgroup$ Commented Oct 13, 2018 at 20:54

2 Answers 2


At the time when the 1-millionth question was actually posted, a screenshot was taken, see (scroll down) here , see also below. As noted by Isabella, this was Separation Properties in Topology.

I agree that the person posting this question didn't win a lottery and didn't do anything special. However, math stack exchange has more than 1,000,000 questions now, somebody posted the 1-millionth question, and that is worth celebrating as celebrations always take place at symbolic events. Why celebrate it?: I admire the countless energy, devotion and, at so many instances, brilliance of the work done here by so many, voluntary work.

Here is the screenshot (courtesy of wolfies):

enter image description here


As already mentioned in the comments, the 1000000th question will change over time. For example, depending on deletions/undeletions, migrations here/away etc. It also depends on your definition - do you want to count closed question? Do you want to order the posts by id or by CreationDate? (This can make a difference for migrated question, for example the question Would Relational Calculus be Turing-Complete if it Allowed Unsafe Queries? is older than the question with the id 1: What Does it Really Mean to Have Different Kinds of Infinities?) Do you want to include the locked questions? Do you want include the deleted questions? Do you want to include questions which have been migrated here - and originally asked elsewhere?

There is a somewhat similar question on Meta Stack Overflow: What was the 10 millionth question? One of the answers there provides a solution using API. Here is the link: https://api.stackexchange.com/2.2/questions?page=1000000&pagesize=1&order=asc&sort=creation&site=math The question given there will be changing over time.

It is also possible to try do this using Data Explorer. Again, the 1000000th question will change over time, each time the post shown there will correspond to the state at the most recent update of the data in the database. Here are a few such queries (which definitely can be improved/modified in many ways):

At the moment, the above queries will come out empty, since at when the database was updated there were less than 1000000 questions. The exception is the query that includes deleted questions. But you can change the numbers and play around with the queries - for example, you can look at 100000 question and compare this with the comment posted at the time: Congrats, Math.StackExchange.com!

  • $\begingroup$ I will add that some short discussion related to those queries can be found in the Data Exploerer chatroom. $\endgroup$ Commented Oct 8, 2018 at 12:32
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    $\begingroup$ Mention of the threshold crossing, without specific identification of a particular Question, has already been added to the Milestones post (Math.SE History). That is sufficient commemoration for my purposes (taken with the special can of juice saved for the day). $\endgroup$
    – hardmath
    Commented Oct 9, 2018 at 15:46
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    $\begingroup$ @hardmath I agree that it's merely a curiosity and actually the question which is in the n-th position among existing question can change over time depending on (un)deletions. Still, if there is an oportunity to mention useful tools such as SEDE and API why not use it - it might be new information for some users. (And, as the links above show, there were similar posts for 100k questions here and for 10 millions on meta.SO. In fact, judging by existence of a separate tag, it seems that it was discussed quite a lo there.) $\endgroup$ Commented Oct 9, 2018 at 23:19
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    $\begingroup$ Thanks. Any reasonable definition of "millionth question" would be fine with me. This is history/sociology, not mathematics, so fretting about fuzzy definitions seems inappropriate. The definition that I had in mind was: which question caused the counter at the top of the main question page to reach 1,000,000 for the first time. Apparently it was Firat Celebi's "Separation Properties in Topology" question. $\endgroup$
    – bubba
    Commented Oct 10, 2018 at 12:43
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    $\begingroup$ By that definition, it seems it appears that the millionth was Firat Celebi's "Separation Properties in Topology" question. There's a screen shot in this answer math.meta.stackexchange.com/questions/7021/…, $\endgroup$
    – bubba
    Commented Oct 10, 2018 at 12:52
  • $\begingroup$ @bubba When you are talking about the screenshot, I suppose that you wanted to link to this answer rather than this answer. The screenshot is: i.sstatic.net/wHLjd.png $\endgroup$ Commented Oct 10, 2018 at 12:54
  • $\begingroup$ @MartinSleziak. Actually, the same screen shot is included in both answers, but it's certainly easier to find in the one you cited. $\endgroup$
    – bubba
    Commented Oct 11, 2018 at 1:57

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