Free Printable Prime Numbers Worksheets
Prime or composite · Factorization · GCD · LCM · Sieve of Eratosthenes — Free
Generate custom prime numbers worksheets to print as PDF or practice online with automatic grading. Includes a factor tree checker, interactive Sieve of Eratosthenes and prime tables up to 1000. Free and no registration required.
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🔍 Prime number checker
Enter any number and get its factorization with a factor tree.
🧮 Interactive Sieve of Eratosthenes
Cross out multiples of each prime to discover all primes up to 100. Click a number to cross it out.
Prime number tables
Printable tables with highlighted primes. Each table can be downloaded as PNG or shared via WhatsApp.
Prime numbers from 1 to 20
Prime numbers from 1 to 50
Prime numbers from 1 to 100
Prime numbers from 1 to 200
Prime numbers from 1 to 500
Prime numbers from 1 to 1000
What are prime number worksheets for?
Prime numbers are the fundamental building blocks of arithmetic. Every integer greater than 1 can be uniquely expressed as a product of prime numbers (Fundamental Theorem of Arithmetic). Understanding primes is essential for calculating GCD, LCM, simplifying fractions and understanding modern cryptography.
Recommended routine: start by identifying primes (prime or composite?), then practice factorization, and finally use the factors to calculate GCD and LCM. The Sieve of Eratosthenes is the best visual exercise to understand how primes are distributed.
📌 Key concepts
Prime numbers
A prime number has exactly two divisors: 1 and itself. 2 is the only even prime. 1 is neither prime nor composite.
Prime factorization
Every composite number can be written as a unique product of primes: 60 = 2² × 3 × 5. Divide by 2, then 3, 5, 7… until you reach 1.
GCD (Greatest Common Divisor)
Multiply the COMMON prime factors with the SMALLEST exponent. GCD(12,18) = 2¹ × 3¹ = 6.
LCM (Least Common Multiple)
Multiply ALL prime factors with the LARGEST exponent. LCM(12,18) = 2² × 3² = 36.
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