1, and the counting units of each level are: 10, 100, 1000.

2. The counting units of ten thousand categories are: ten thousand, one hundred thousand, one million and ten million.

3. Billion-level counting units are: billion, billion, billion, and hundred billion.

4. Every four digits are one level.

5. Units, 10, 100 and 1000 are all grades.

Six, ten thousand, one hundred thousand, one million, ten million is ten thousand.

7. Billions, billions, billions is billions.

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