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Prime Factorization (Medium)

AMC 10/12 mid (≈Q9–16) — multi-step.

Prime Factorization: core idea

Divisor function.

Example problem: hint and answer

How many positive divisors does 23⋅32⋅52^3\cdot3^2\cdot5 have?

Hint: Track each prime exponent independently. Answer: 24.

Practice (9 problems — type your answers)

  • 1. Find gcd⁡(84,126)\gcd(84,126).

  • 2. Find lcm⁡(45,60)\operatorname{lcm}(45,60).

  • 3. How many perfect-square divisors does 360360 have?

  • 4. What is the least nn such that 72n72n is a perfect square?

  • 5. How many positive factors of 10001000 are multiples of 1010?

  • 6. Find the sum of the prime factors of 462462.

  • 7. What is the greatest square dividing 540540?

  • 8. How many divisors of 24⋅332^4\cdot3^3 are divisible by 1212?

  • 9. Find the least positive integer with exactly 66 positive divisors.

Prime Factorization Practice Problems — Medium