In a recent answer of mine, I noticed that a chain of equations renders correctly on my laptop but incorrectly on iPad and iPhone. The iPad/iPhone treats a particular number as if it is a phone number. It then inserts a FaceTime link which messes up the LaTeX/MathJax rendering, making the answer unreadable. The number is $1664474849$, which appears in the numerator calculation of $q(5)$ here:

Coin Flip Problem

I could likely play around with different ways to type my equation, but I leave it as-is so you can see the issue for yourself (if you view from iPad/iPhone).

Question/comment: This seems to be a larger issue that could affect many questions/answers. It may already be affecting one of your own questions/answers and you do not know it because you only use a laptop. It may also annoy people who happen to have those phone numbers. Can something be done to fix the general problem?

Edit: I notice that for this question, the number I typed above is rendered without the incorrect FaceTime link even on iPad...I don’t know why. Perhaps the bug only occurs when the number is in \begin{align} equations rather than dollar signs.


1 Answer 1


@XanderHenderson is right, this is a built-in feature of iOS; since the number of people looking for pizza delivery with their iPhone dwarfs the number of people doing Mathematics with it by a few orders of magnitude, they deemed it useful to convert everything that looks like a phone number into a phone link. The feature does take the context of the number into account, which is why not all 10 digits numbers starting with a 1 are 'linkified', but apparently it's not that smart. The bad news is that you can't turn it off as a user but it'll probably come in handy outside your professional life.

A workaround might be to insert a \hspace{0pt} somewhere in the number, as I did here in the Sandbox (sorry for the edit to your post, that happens when you're editing three posts at once...). It renders correctly for me on iOS, and even copy/pasting works fine. I'm not sure if there are any other side effects.

Since 1664474849 is a typical US phone number format, one might wonder if changing the language/region setting would help, but my iPhone (language: English/United States, region: the Netherlands) detects both those and a more typical Dutch phone number like 0612345678.

  • $\begingroup$ Thanks, I will likely implement your \hspace{0pt} solution in a few days after any residual answers to this question may come in. $\endgroup$
    – Michael
    Jun 19, 2020 at 6:22

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