Meaning of the word "speaking of which" in English

What does "speaking of which" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

speaking of which

US /ˈspiːkɪŋ əv wɪtʃ/
UK /ˈspiːkɪŋ əv wɪtʃ/

Idiom

used to introduce a comment or question about something that has just been mentioned

Example:
I saw Tom yesterday. Speaking of which, did you hear about his new job?
The meeting is at 3 PM. Speaking of which, have you prepared the report?