Twenty-seven is 3x3x3 and as such suggests Divine perfection with emphasis. It is the number of books in the New Testament, whereas in the Old Testament there are strictly 36 (Kings, Chronicles and Samuel having been each one originally, and not two); thus 36, i.e. 3x12, would relate rather to the Divine perfection in government, while 27, i.e., 3x3x3, would speak of the Divine in its own intense force, viz., love, or it would speak of God acting in grace.
Is there any connection with this in the fact that the mercy seat is mentioned 27 times in the Old Testament? The candlestick also 27 times.