Back to Mathematical Olympiad
Difficulty: 3/102024 IOQM 2024 (Q1)

The smallest positive integer that does not divide is:

Guide / Hint

Hint 1: Find the prime factorization of the product of numbers from 1 to 9 (which is ).

Hint 2: Check if each integer starting from 1 can be formed using the prime factors with exponents at most respectively.

Hint 3: Notice that 11 is a prime number and is not present in the prime factors of .

Solution

Let .
The prime factorization of is:

We test positive integers in increasing order starting from 1:

  • All integers from 1 to 10 only have prime factors 2, 3, 5, and 7, and their exponents are smaller than or equal to those in . For example, , which divides .

  • The next integer is 11, which is a prime. Since 11 does not appear in the prime factorization of , it cannot divide .

Therefore, the smallest positive integer that does not divide is .

Ready to track your progress and master these topics?

Create a free account