In uk.telecom.mobile Pamela wrote:
A web site sends you 6-digit number to your phone to check your ID. Do
you memorise this by saying to yourself: 12-34-56 or 123-456?

It's a genuine question to see what number span people are using to
remember random numbers.

It depends on the structure of the number. eg:

55-67-99
132-231
1000-44
9-88888
27-288-9

etc

Theo