College+ · Number Theory

Primes & factorization

100 problems in this skill, each with a solver-verified answer key. Answers are checked the moment you submit — with a hint if you want one and a worked solution afterwards.

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A few statements from this skill. Answers, hints and worked solutions live in the practice session.

Warm-up
The prime-counting function $\pi(x)$ counts the primes not exceeding $x$ . Compute $\pi(40)$ .
Warm-up
The prime-counting function $\pi(x)$ counts the primes not exceeding $x$ . Compute $\pi(84)$ .
Warm-up
The prime-counting function $\pi(x)$ counts the primes not exceeding $x$ . Compute $\pi(78)$ .

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