The greatest odd factor of the product $$1\times 2\times 3\times 4\times 5\times 6$$ is． 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Basic Concepts of Factors and Multiples
$$1\times 2\times 3\times 4\times 5\times (2\times 3)=2\times 4\times 2\times (1\times 3\times 5\times 3)=16\times 45$$. 