I have already finished my Mathematics Ph.D. application form for several universities. However, I noticed that my email address in my CV and personal information contains the number "666", which, I recently learned, is the number of devils. I'm not a native speaker of western countries. I'm from Asia and "666" means auspicious in my language. I've used this email address to apply for Ph.D. programs at several universities in Germany and the U.S. I'm wondering whether this would make me get rejected by universities' committees.
I would find it extremely surprising if a European reacts very negatively to 666. Most people would be somewhat aware of a connection to "The Beast" in the biblical book of revelations, but they wouldn't really care. (I've grown up in Germany and spend most of my career in the UK, for reference.) On the other hand, it does not seem to be that rare for people in the US to feel eg uncomfortable with a bill of $6.66, and to buy a little bit extra to avoid it. But even in the US, I expect that the overlap between people doing that and people sitting on admission committees for Math grad schools is small.
Your email address isn't really what people evaluate, and most will just ignore it. Having numbers in your email address may be read as a little unprofessional. If someone notices the 666 they might think you're trying to be a bit edgy by flirting with satanism, but almost no one would care. People applying for PhDs tend to be young, and thus have a decent excuse for appearing a bit unprofessional and/or trying to be edgy.
While I agree with the answer of Arno that this shouldn't be a problem, there is a technological fix.
It is probably easy for you to create a new email address, say at Gmail, and forward everything from either of them to the other, as you choose.
FWIW, there are other numbers with negative interpretations, 88 for example. And some email systems generate addresses with numeric elements as well.
Applying from an academic institution's email address is sometimes advantageous (minimally) and you might be able to get one from your current institution for purposes of application. You will probably get a new one from any institution you join in the future.
If you are a member of a professional society in your field then they might also make it possible to use an email address with the association name: [email protected], say (UnderwaterBasketWeavers).
A side aspect not mentioned so far but very important is the remainder of the email address.
Based on my experience, any email address not containing your name, some abbreviation of your name, or being from a professional (e.g., university/personal) domain could easily be perceived as unprofessional, i.e., seen as your spam/childhood/teeny email address. However, perception might vary vastly depending on the professional area and their culture. I.e., computer scientists would most likely not care if the email itself is sufficiently professional, whereas law professionals might have an entirely different attitude. Given that you say math I would suspect a reaction closer to computer science than to law.
While you may not be flat-out rejected for using '666', it is possible it may be interpreted differently from what you fear. Namely, without knowing you or the reason behind your choice, some people might think you as "cheeky", as some kid trying to be "a bad kid", similar to the style of some heavy metal bands. Such bias might have some negative effect; for example, while they will not avoid talking to you when you talk to them, someone might avoid initiating contact, or might avoid joint work, etc.
I suggest for applications going forward, change. Anything that distracts from your merits as a student should not be present on your application. While the odds are low that anyone will even see it, getting a new email address is fast and easy.
OTOH, if you already sent them in, don't worry about it.
It's like a first date with someone you really like. Do you wear your old ratty shoes that she would be fine with if you were dating? Or do you want to wear your nicer shoes on your first date to make a good first impression? Most people would wear their nicer shoes.
It's not a big deal, but say if even 1 in 200 applications get rejected for it, do you want to lose that chance? I wouldn't. I would have a slightly more professional email address to use.
BTW this wouldn't be offensive to anyone in academia, but it's an "edgy" thing that a teenager might put in their gamer tag. If it affects your application it will be because it will give an appearance of silliness and immaturity when you are applying for something very serious.
If they think you thought it was amusing to choose an email address with 666 in it, then yes, it could work against you. They won't have the fact that it's considered auspicious in some Asian cultures uppermost in their minds.
If on the other hand it's clear that's it's an institutional address and you just happen to have been allotted the number 666, without you having any say in the matter, that's different. I don't think that would affect how they consider your application one way or the other. (In Asia, though, it would probably be to your benefit.)
All of these comments in my opinion dancing around the issue. If you feel for one second this may have an impact on your potential admission to these Universities, go with your GUT and just make a new email solely for applying for these things. It takes two seconds to do and all of your doubt/fear is eliminated instantly. With respect to the ones you have sent though, It could have an impact and it could not have an impact. While we would all hope to live in a perfect world where these things do not matter, we don't, and especially in the United States, people will kill/lie/cheat/ect for their religion. It is just safer to make a new one, but don't worry about the ones you have already sent out.
From the general mood and trends of comments and answers, it seems to that the majority of people in Academia:SE never had to deal with the pious, white collar America.
In short: as long as you are dealing with academics, whether you have 666 or Satan or Iblis or Shaytan or Mara in your email, you will be fine. As soon as your email is screened by someone non-academics (for example: secretary office of some full professor, secretary office of some head of department), in some "burocratic" functions, your email is most likely already involuntarily screened out by the spam filter set up for the institution (may apply also to academics) or voluntarily sent to the spam folder.
Email was born as an informal mean of comunications for nerds, it became a super formal way to reach out to people. Please remember that whatever you write in an email is, in general, forever reachable and readable by everyone ([think of an email as a postcard])2 .
The western world expects the email to be in the format
[email protected]/.org/.edu .
Anything else is likely to be filtered out by AI-powered algorithms or pious-powered secretaries.
Yeah no... This isn't going to be seen as controversial by any respectable institution.
In Europe, it's entirely a non-issue since society is basically secular.
Even in the the United States, you should be fine as academics tend not to be religious fanatics. If you do have any issues because of it, you probably wouldn't have wanted to work in those institutions anyway.
It's also worth adding that discriminating against someone on the basis of them potentially being a Satanist would be massively illegal in basically every western nation.