#[05AB1E](https://github.com/Adriandmen/05AB1E), <s>8</s> <s>6</s> 5 bytes

_Thanks to @quartata for 2 bytes off (square-root function), and to @Adnan for the 1 more byte (join-by-newline function)_

    Dgtô«

[__Try it online!__](http://05ab1e.tryitonline.net/#code=RGd0w7TCqw&input=TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtdA)

###Explanation

    D     Implicit input. Duplicate
    g     Number of elements
    t     Square root
    ô     Split into chunks of that length
    «     Join by newlines. Implicit display