The integer 2023 is equal to . Which of the following is the smallest positive perfect square that is a multiple of 2023?
Solution
Since , then any perfect square that is a multiple of 2023 must have prime factors of both 7 and 17. Furthermore, the exponents of the prime factors of a perfect square must be all even. Therefore, any perfect square that is a multiple of 2023 must be divisible by and by , and so it is at least which equals . Therefore, the smallest perfect square that is a multiple of 2023 is . We can check that is larger than and that none of and and is a perfect square.
Want a route through all this instead of an archive? The track
puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.