Is there a finite abelian group such that the product of the
orders of all its elements is ?
Solution
No, there is no such group.
By the structure theorem for finitely generated abelian groups,
can be written as a product of cyclic groups.
If any of these factors has odd order, then has an element of odd order,
so the product of the orders of all of its elements cannot be a power of 2.
We may thus consider only abelian -groups hereafter.
For such a group , the product of the orders of all of its elements
has the form for some nonnegative integer , and we must show
that it is impossible to achieve .
Again by the structure theorem, we may write
for some nonnegative integers , all but finitely many of
which are .
For any nonnegative integer , the elements of of order at most
form a subgroup isomorphic to
which has elements for .
Hence
Since , is always divisible by .
In particular, forces .
However, the only cases where are where all of the are ,
in which case , or where for some and
for , in which case .
The right side is a strictly increasing function
of which equals for and for , so it can never equal
2009. This proves the claim.