11. From $1,2, \cdots, 100$ choose $k$ numbers, among which there must be two numbers that are coprime, then the minimum value of $k$ is
11. 51 Choose 51 numbers from $1,2, \cdots, 100$, there must be two that are coprime. Also, in $2,4, \cdots, 100$ these 50 numbers, no two are coprime.