Until this point, we’ve seen:

• Divisors
• Divisibility & remainder
• Primes & prime factorization
• Sieve of Eratosthenes

These are more than enough to understand what GCD and LCM are, and how to find them.

Spider-Mans pointing at each other

GCD, a.k.a. Greatest Common Divisor

LCM, a.ka. Least Common Multiple: GCD’s Elder Brother

A special case: GCD and LCM of $2$ integers

I suggest you always think about prime factorization when dealing with these.

This was the last topic about divisibility (kind of). It’s time to learn how to count!