I am a math major and find math interesting, but I have also really enjoyed my writing classes. I also find that I do very well on writing assignments. I find this weird since most of the math people I know hate writing. However, I do still hate to read.
Not weird. I’m an engineering major who writes for fun.
Absolutely not weird. My math-major boyfriend and I (I’m engineering) both love writing, and I do a lot of music and musical theater stuff. A lot of people seem to think that if their into one thing they have to be exclusively into that thing, which is totally not true. And if you like writing and are good at it, you’ll find projects so much easier, especially in math–there are more words than numbers in a good mathematical paper, from what I’ve seen.
Not weird at all and it offers many opportunities. This is a very timely questions – I was just reading Isaac Asimov’s wiki yesterday and it describes how he combine his love of science and writing, both fiction and non fiction. Take a look at his wiki, where it refers to some books about his life that may open up some ideas to you.
If it’s weird, then I’m weird. But weird is cool. 
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@TheAverageJoe71 math has a lot of writing (particularly with proofs, research papers, etc.). Also a lot of reading.
The stereotype is that STEM people are not good at writing or critically analyzing what they read. What I’ve seen through the years is there is some truth in that, and finding people who can understand STEM fields and who can also communicate effectively both in writing and presentation is extremely valuable. It opens up more doors into future career paths.
D is a STEM major and does very well in math. She also got the English award at HS graduation because she is a great writer.
I would say your writing ability will be a total asset for a math person - a lot of STEM people out there who are TERRIBLE communicators. Someone like you could be an excellent teacher: having a grasp of and enthusiasm for the subject matter and being able to convey it to others in a clear and meaningful way. Or a writer on mathematical subjects for publications/blogs/etc.
Another famous person who combined STEM and writing: Michael Crichton. Medical degree and best-selling author, screenwriter, director, producer, etc., etc. Passed away way too early, but he sure burned bright while he was here.
No, OP, you are not weird. Embrace your diverse interests/abilities - you are a Renaissance person!
Why would it be weird?
I’m a historian who works a LOT with big data so I use advanced statistics almost as much as I write- and it’s a write or die industry.