At least one person in the world has studied from my notes every single day since 2013. These Number Theory notes are part of that library.
Number Theory was a math elective in my third year, second semester, at BITS Pilani, Dubai Campus. It sits at an interesting edge: deep enough to be serious mathematics, applied enough to matter to an engineer.
The notes cover divisibility, prime numbers, modular arithmetic, Diophantine equations, and applications to cryptography. There is a lot of territory for a single elective, and the notes work through all of it.
There is also a second set of Number Theory notes on this site, by Ronak Sumbaly.
I started putting notes online in 2013 as an undergrad, with one idea: if you have something useful, put it where people can reach it. The PDF is embedded on this page: read it here, or download it to keep. Learn. Share. Repeat.