I just finished my first undergrad course in Number Theory. I really like it, but now I'm wondering what applications of elementary number theory there are beyond cryptography. Specifically, are there any resources I can look at linking number theory to the physical sciences (phys, chem, bio, etc)? -- I'm still an undergrad so it would need to be relatively gentle for me to jump into it now (I've taken the standard courses in Abstract Algebra and Real Analysis, but nothing else really, yet). Is there anything that fits the bill?