partial numbers are all prime
Source: Azerbaijan NMO 2023. Junior P1
August 24, 2023
number theoryAZE JUNIOR NATIONAL MO
Problem Statement
For any natural number, let's call the numbers formed from its digits and have the same "digit" arrangement with the initial number as the "partial numbers". For example, the partial numbers of are and the partial numbers of are Find all natural numbers whose partial numbers are all prime. Justify your opinion.