The greatest odd factor of $$30$$ is ． 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Basic Concepts of Factors and Multiples
The factors of $$30$$ are $$1$$, $$30$$, $$2$$, $$15$$, $$3$$, $$10$$, $$5$$, $$6$$, so the greatest odd factor of $$30$$ is $$15$$. 