Is there a name for when you read two or more digits together rather than as a single number?

A list of digits read one by one is a string. From Wolfram MathWorld:

string: A string of length n on an alphabet l of m characters is an arrangement of n not necessarily distinct symbols from l. There are m^n such distinct strings.

For example, the strings of length n=3 on the alphabet {1,2} are {1,1,1}, {1,1,2}, {1,2,1}, {1,2,2}, {2,1,1}, {2,1,2}, {2,2,1}, and {2,2,2}.

For example, when one of your financial accounts requires identity verification, it may send you a six-digit code via email or text, e.g., 418967, which you have to enter into your computer or phone to access your account. 418967, when read digit by digit, is a six-digit string on the alphabet {0,1,2,3,4,5,6,7,8,9} of 10 characters, i.e., {4,1,8,9,6,7}.

So, in reading digits one by one, one is reading them as a string.

My guess is that reading these digits, as integers up to 9 (in number base ten), is the straightforward, goes-without-saying, regular way to read a such numerals. I would call it punctuating the digits with commas, etc, to give the long form of a numeral. Any word such as punctuating, drawing out, delineating.

Here's a related thread, which I came across, a few months ago. The idea is to also pronounce numerals the way "spelled out".

Why don't years have commas?

Perhaps, there is error-checking value to both these, and the other, approaches to working with numbers.