20. Find how many zeros are at the end of the decimal expression of 120!. 

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。 

Note: The note above is not part of the translation but is provided to clarify the instruction. The actual translation is above it.
20. Find the highest power of 10 that divides 120!, which is also the highest power of 5 that divides 120!. Therefore, there are 28 zeros.