Sorry, yes, 41m-on-a-side cube, not 41m^2-sided cube. The outermost square-root in the expression takes the area of one side of the cube (which is the area of the dollars, divided by 6 to account for needing to cover the 6 sides of the cube) and pulls it down to the cube's length of one side.
Yeah, you said it correctly, but I'm not a native speaker and brainfarted "41m on a side" into "each side is 41 sqm". I thought "face", rather than "edge".
