Belgian National Number is your birth date, then an increment from 1 to 999 for every baby born that day, then a base-97 checksum.

port11 18 minutes ago | parent | next [-]

Are there never more than 1k babies born in a day?

andruby 20 hours ago | parent | prev [-]

Not sure if still the case: odd numbers for males and even numbers for females.

This also means a person’s Belgian RRN can change.

Yep, but they do not change on sex change, IIRC.

	▲	andruby 10 hours ago \| parent [-]
		I wrote a system for a medical lab decades ago and IIRC I did actually have to change some RRN's manually. It's been a while so I'm not 100% sure, but I do think the changes were due to switching gender.