12.已知等比数列{an}\{a_{n}\}{an}的各项均为正数,公比q≠1q\ne 1q=1,a1a2⋯akk=a11\sqrt[k]{{a}_{1}{a}_{2}\cdots {a}_{k}}=a_{11}ka1a2⋯ak=a11,则k=(k=(k=( )))