In mathematics, a perfect number refers to a number where the sum of its divisors, excluding the number itself, equals the number.

He is immersed in the study of panmagic squares.

This fish is completely farmed, and no capture is done in the natural environment.

He grew up in a region where Mandarin is not very common.

Do you know this secular speech?

We practice conversation every day.

The dialogue with him is always fun.

He and I held a meeting to settle the matter.

He and I finally came to terms.

He often tells interesting yarns.