We say that a positive integer is super odd
Source: May Olimpiad 2020 L2 P1
November 27, 2020
number theory
Problem Statement
We say that a positive integer is super odd if all of its digits are odd. For example, 1737 is super odd and 3051 is not. Find an even positive integer that cannot be express as a sum of two super odd numbers and explain why it is not possible to express it thus.