2. (3 points) Spring Bud Cup + Spring Bud Cup $=578$, "Spring Bud Cup" can represent the number $\qquad$

Translate the above text into English, please retain the original text's line breaks and format, and output the translation result directly.
【Answer】Solution: Spring Bud Cup + Spring Bud Cup $=578$,
Then: Spring Bud Cup $\times 2=576$,
Spring Bud Cup $=576 \div 2=289$;
Therefore, the answer is: 289.