Courses

Number Theory

Grades 9–12
All Dates and Tuition
Modality
In Person
Identification Level
Quantitative - CTY-Level
Tuition
$6,969 - $7,801

About the Course

Called "The Queen of Mathematics" by the great mathematician Carl Friedrich Gauss, number theory is the study of the natural number system from which all others are derived. Despite the simplicity of the natural numbers, many accessible problems in number theory remain unsolved. For example, the Goldbach Conjecture, formulated in 1742, which posits that every even integer larger than 2 is the sum of two prime numbers, has defied all proof attempts. In this proof-based course, you'll learn the major ideas of elementary number theory and the historical framework in which they were developed. While strengthening your ability to analyze and construct formal proofs, you and your classmates will explore topics such as the Euclidean Algorithm and continued fractions, Diophantine equations, Fibonacci numbers and the golden ratio, modular arithmetic, Fermat's Little Theorem, and RSA public key cryptography. You'll leave the course with an appreciation for the elegance of theoretical mathematics and the ability to craft rigorous arguments.

Typical Class Size: 16-18

Learning Objectives

  • Elaborate, construct, and solve problems of primes using unique factorization, congruences, divisibility, Diophantine equations, primitive roots, and quadratic reciprocity rules
  • Elaborate, construct, and solve problems using sums of squares, number-theoretic functions, continued fractions, and apply to public-key encryption, and elliptic curves
  • Demonstrate competence with modular arithmetic and apply to Diophantine equations
  • Solve Diophantine equations and decide on whether solutions for them exist
  • Explain the role of primes, their central role in arithmetic problems and be knowledgeable about primes in number systems other than integers
  • Proficient at solving primitive root problems
  • Formulate rigorous proofs and defend techniques and theories applied to proofs

About Advanced Enrichment courses

These courses offer above-grade-level material that is presented in a novel context, explored with other advanced learners, and guided by a CTY educator to help prepare students for higher-order thinking and college-style academic challenges. Students work individually and may finish the course early if they complete all requirements before the course end date.

Requirements

CTY courses have grade-level requirements and most require minimum test scores. Some courses may also have prerequisites.

Identification Details
Grade 9–12
Identification Level
Quantitative - CTY-Level
Coursework Prerequisites
Successful completion of Geometry or Honors Geometry and Successful completion of Algebra II or Honors Algebra II

Dates and Tuition

All CTY courses require you to create an account and confirm Identification Level before enrolling can be completed.

In Person

Residential Site icon Residential Site
Summer A 2026
Jun 21, 2026 - Jul 10, 2026
$7,801 Residential
$6,969 Commuter

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Register by: June 11, 2026

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Time Commitment:

Summer B 2026
Jul 12, 2026 - Jul 31, 2026
$7,801 Residential
$6,969 Commuter

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Register by:

Register by: July 2, 2026

Filling up fast! 3 spots left
Time Commitment:

Time Commitment:

Registration Fee and Financial Aid

Tuition and fees will be waived or reduced for students who qualify for financial aid.

Learn more about Financial Aid
Join Fee $55

If you are not a member of CTY yet, you are required to join before enrolling in a course.

Join CTY
In-Person registration fee $75

Non-refundable fee for in-person courses.

Online Registration Fee $15-$20

Non-refundable fee for online courses.

Mathematics

Sharpen your skills and build confidence while solving puzzles, exploring patterns, preparing for competitions, and tackling real-world problems in a rigorous and fun classroom.  

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