4. (10 points) As shown in the figure, 5 identical small rectangular prisms are exactly assembled into a rectangular prism with a volume of 22.5. Then, the sum of all edge lengths of one small rectangular prism is.
22
【Analysis】According to the graph, we can get length $=3 \times$ height, length $=2 \times$ width, length: width: height $=6: 3: 2$. Let the length of the cuboid be $6 x$, the width be $3 x$, and the height be $2 x$. Therefore, the volume of a cuboid is: $6 x \times 3 x \times 2 x=36 x^{3}$. From this, we can find the cubic value of $x$, and then the value of $x$, and finally, the sum of the lengths of the edges of the cuboid can be calculated.
【Solution】Solution: According to the graph, we can get length $=3 \times$ height, length $=2 \times$ width,
length: width: height $=6: 3: 2$, let the length of the small cuboid be $6 x$, the width be $3 x$, and the height be $2 x$.
Therefore, the volume of a small cuboid is: $6 x \times 3 x \times 2 x=36 x^{3}$
$$
\begin{aligned}
180 x^{3} & =22.5, \\
x^{3} & =0.125, \\
x & =0.5 ;
\end{aligned}
$$

length $=0.5 \times 6=3$, width $=0.5 \times 3=1.5$, height $=0.5 \times 2=1$,
sum of edge lengths $=(3+1.5+1) \times 4=22$.
Answer: The sum of all the edge lengths of a small cuboid is 22.
Therefore, the answer is: 22.