
What are Number Theory Concepts?  Quora
Number theory studies integers, that is, whole numbers, and their relationships. Principle concepts include square numbers and higher powers of numbers.
https://www.quora.com/Whatarenumbertheoryconcepts

Number Theory  Basic Mathematics
My website will teach you the basics of number theory.
http://www.basicmathematics.com/numbertheory.html

Unsolved Problems in Number Theory  Wikipedia
Unsolved problems in mathematics in the field of number theory.
https://en.wikipedia.org/wiki/Unsolved_Problems_in_Number_Theory

Intro to Number Theory Part 1  YouTube
Introduction to Number Theory and the Fundamental theorem of arithmetic.
https://www.youtube.com/watch?v=FirJVPVSPh4

Discrete Mathematics/Number Theory  Wikibooks
Unlike real analysis and calculus which deals with the dense set of real numbers, number theory examines mathematics in discrete sets, such as N or Z. If you are unsure about sets, you may wish to revisit set theory.
https://en.wikibooks.org/wiki/Discrete_Mathematics/Number_theory

Where is Number Theory Used in the Rest of Mathematics?
Where is number theory used in the rest of mathematics? This question is answered here at Math Over Flow.
http://mathoverflow.net/questions/90700/whereisnumbertheoryusedintherestofmathematics

What is Number Theory?  How Stuff Works
What is number theory? Learn how mathematicians use number theory to define relationships that underlie nature itself.
http://science.howstuffworks.com/mathconcepts/numbertheory.htm

An Introduction to Number Theory
In this article we shall look at some elementary results in Number Theory, partly because they are interesting in themselves, partly because they are useful in other contexts, and partly because they will give you a flavour of what number theory is about.
https://nrich.maths.org/4352

Number Theory  Britannica
Branch of mathematics concerned with properties of the positive integers. Sometimes called "higher arithmetic," it is among the oldest and most natural of mathematical.
http://www.britannica.com/topic/numbertheory

Number Theory  Wikipedia
Number theory or arithmetic is a branch of pure mathematics devoted primarily to the study of the natural numbers and the integers.
https://en.wikipedia.org/wiki/Number_theory