[martyvis]

FYI 2600 and 2.6k use the same number of characters.

[ramenbytes]

Could use the electronics convention and save a character: 2k6

[Bootvis]

It doesn't mean the same though, 2.6k implies somewhere between 2550 and 2650 years ago and 2600 an exact number of years.

[timeon]

I would guess that sentence: "that sank 2600 years ago" would imply that we are not talking about exact date. But more explicit word like: "that sank about 2600 years ago" would help.

Using different number formatting instead of word or sign (~) is still implicit and not explicit.

[zos_kia]

That is intriguing I had never seen xk used in that sense. Is that a common convention?

[kstrauser]

2600 only has 2 significant digits. It's not an exact number.

[stevage]

Has the advantage that you can't confuse it with 2600BCE.