Please use the word “digress” : leave

the main subject temporarily in speech or writing.

I can’t say

that the square root of 225 is 25. In your example, “I’m certain of it: the square root of 225 is 25,” said Peter. When Mary pulled out her phone and used the calculator app to find that it was in fact 15, Peter recoiled. “Such a clever and funny story that brought back memories for me, involving Euler and how I can explain

it…” At once as we chatted for a long time, he smiled at his comments.