Shuffles to restore the deck

A $52$-card deck is shuffled as follows: split into positions $1$–$26$ and $27$–$52$, then interleave so the bottom half ($27$–$52$) takes the odd positions $1, 3, \dots, 51$ and the top half ($1$–$26$) takes the even positions $2, 4, \dots, 52$. What is the minimum number of such shuffles needed to return the deck to its original order?