
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
According to relevant data, from January 2014 to December 2014, the total fiscal revenue of Gao'an City was about 21 billion RMB. The number "21 billion" is represented in scientific notation as ____.

Present the answer in LaTex format: \boxed{Your answer}
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