The "apothem is a perpendicular from the vertex of a pyramid on a side of the base."
A peculiarity of this pyramid is, that base is to altitude as apothem is to half base.
In any pyramid, the apothem is to half the base as the area of the four sides is to the area of the base.
I have mentioned the above to show how very nearly these ratios agree with my exact ratio of 21 to 34 half base to apothem.