Always wondered why the cuil/cuit has those two extra digits at the beginning and one extra digit at the end. So I have just googled it:
The one digit suffix is a verification digit. It is generated with the first 10 digits by using modulo 11 (see
https://en.wikipedia...iki/Check_digit for details about modulo).
The two digit prefix works (or worked?) as follows: 20 for men, 27 for women. And in special cases 23 or 24 for both. This might have changed, though. I ran across several pages mentioning that the prefix no longer depends on the gender and 27, 20, 23 and 24 are issued for all, now. (example:
https://es.wikipedia...icación_Laboral ).