Factors, multiples and primes

List all the factors of $36$, separated by commas.

Which sentence is true?

Is the number $1$ prime, composite, or neither?

Which of these numbers are prime? (Choose all that apply.)

What is the greatest common factor of $24$ and $36$?

In Nairobi, one bus leaves the station every $4$ minutes and another every $6$ minutes. Both leave together right now. After how many minutes do they next leave together?

Which of these writes $84$ as a product of primes?

Use the digit-sum test. Which of these numbers are divisible by $9$? (Choose all that apply.)

Lean writes b ∣ a to mean "$b$ is a factor of $a$", that is, $a = b \times k$ for some $k$. Which Lean statement says that $3$ is a factor of $12$?

Write is_prime(n) that returns True if n is prime and False otherwise. Try every possible factor d from 2 upwards, but stop as soon as d * d > n (the lesson explains why that is enough). The starter uses the mistaken idea that odd numbers are prime, so the tests fail.