Mathematics
Grade 10
15 min
Prime or composite
Prime or composite
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define prime, composite, and the number 1 with mathematical precision.
Apply the Fundamental Theorem of Arithmetic to uniquely decompose any integer greater than 1.
Efficiently determine if an integer 'n' is prime by testing for divisibility by primes up to the square root of 'n'.
Construct a logical argument or simple proof related to properties of prime and composite numbers.
Use prime factorization to find the Greatest Common Divisor (GCD) and Least Common Multiple (LCM) of integers.
Analyze the relationship between prime factorization and the number of divisors an integer has.
Ever wondered how your online data is kept secret? 🤫 The security of modern digital encryption relies heavily on the properties of extremely large prime num...
2
Key Concepts & Vocabulary
TermDefinitionExample
Prime NumberA natural number greater than 1 that has exactly two distinct positive divisors: 1 and itself.The number 17 is prime because its only positive divisors are 1 and 17.
Composite NumberA natural number greater than 1 that is not prime. It has more than two distinct positive divisors.The number 30 is composite because its divisors are 1, 2, 3, 5, 6, 10, 15, and 30.
The Number 1A unique natural number that is neither prime nor composite because it has only one positive divisor: itself.The number 1 has only one divisor (1), failing the two-divisor requirement for primes and the more-than-two requirement for composites.
Prime FactorizationThe process of expressing a composite number as the unique product of its prime factors.The prime factorization of 84 is 2 ×...
3
Core Formulas
Efficient Primality Test
To determine if an integer `n` is prime, one only needs to test for divisibility by prime numbers `p` such that `p ≤ √n`.
Use this rule to avoid unnecessary checks when testing large numbers. If `n` has no prime factors less than or equal to its square root, it must be prime.
Number of Divisors Formula
If the prime factorization of a number `n` is `n = p₁^{a₁} * p₂^{a₂} * ... * pₖ^{aₖ}`, then the total number of positive divisors of `n` is `d(n) = (a₁ + 1)(a₂ + 1)...(aₖ + 1)`.
This formula allows you to calculate the total number of divisors a number has without listing them all. It is derived from the exponents in the prime factorization.
4 more steps in this tutorial
Sign up free to access the complete tutorial with worked examples and practice.
Sign Up Free to ContinueSample Practice Questions
Challenging
What is the smallest positive integer `k` such that the product `1260 * k` is a perfect cube?
A.25
B.50
C.75
D.150
Challenging
A number `N` has the prime factorization `p⁴ * q²`, where `p` and `q` are distinct prime numbers. How many positive divisors does the number `N²` have?
A.45
B.30
C.15
D.90
Challenging
Let `p` and `q` be two distinct prime numbers, both greater than 2. Which of the following statements about their product, `pq`, is ALWAYS true?
A.pq + 1 is a prime number.
B.pq is an odd number with exactly four divisors.
C.pq is an even number.
D.pq has exactly two divisors.
Want to practice and check your answers?
Sign up to access all questions with instant feedback, explanations, and progress tracking.
Start Practicing Free