I used to just read the digits, but some native speakers do it in a different way. They read it 2 by 2. So my house number (1234) would be "twelve thirty-four", and my apartment number (567) "five sixty-seven". When I pay my bills the cashier lady told me the amount due ($121.05) was "one twenty-one dollars five cents". But I've yet to hear anyone read their phone number in this fashion - they just read it digit by digit. So what is the general convention of reading a long sequence of numbers in English?
There's no strict rule about any of these things. There are conventions.
There are two main ways of reading numbers:
- Mathematically, using place value words (hundred, thousand, million, etc)
- Broken up into smaller segments, generally tens or ones.
With long sequences of numbers, particularly those like phone numbers and social security numbers, we don't generally use the mathematical terms because they're number sequences and not whole numbers.
Let's use this one for example and I'll list a couple versions that I would expect to hear. Note, commas indicate a pause:
- two-one-three, five-five-five, four-four-five-five
- two-thirteen, triple five, forty-four-fifty-five
These groupings may be mixed together in many possible configurations, often depending on the person and what the specific number is. Note, while we will go up to tens units, we rarely go up to hundreds in phone numbers.
We will occasionally use "double" or "triple" when numbers are repeated. Though this is more common in British English than American English.
An exception is when you run into phone numbers ending with zeroes, usually either two or three. These numbers are common in corporate/business phone numbers because they're easy to say and remember:
- eight hundred, two-four-four, one thousand.
- two-one-oh, two-three-five, fifty-five hundred
(as a note, the sections read off as individual numbers can be combined as in the earlier example)
Similarly, with other long numbers, we often say each number individually or with the tens units. So, in Social Security numbers, we'll specifically group the numbers and say them in singles or in pairs:
- eight-zero-three, six-two, two-eight-two-seven
- eight-oh-three, sixty-two, twenty-eight-twenty-seven
Exact dollar amounts are generally read in a dollars and cents format using the place values and separating the dollars and cents verbally:
- three thousand seven hundred [and] sixty-five dollars and sixty-six cents.
But we also will often shorten it and ignore the place values and the dollars and cents:
- thirty-seven sixty-five sixty-six
As you can guess, this can be a bit confusing. It's arguably more common with amounts under 1000.
- Three-forty-five nineteen
So, the general convention for long numbers (if you're not reading them mathematically) is to read them in singles or pairs and, if there are three numbers, the first number is generally said alone with the second two paired (if you're pairing them). As a caveat, if a number ends with two or more zeroes, it will often be read as -hundred (two zeroes) or -thousand (three zeroes).
Your question made me laugh, as inside my head, I was reading numbers 2x2 or one at a time just as you had described without even thinking about it. Why? I have a feeling that it comes down to convention and doing as you have heard others do and because reading in pairs quite often uses less syllables are always use less word breaks. Twelve Thirty Four has 4 syllables and 1 word break while one two three four also has 4 syllables, but 3 word breaks thus slowing down speech. We also don't stop at pairs: Often you will hear "1,400" read as "fourteen hundred" instead of "One thousand, four hundred." Even your house number might be read as "twelve hundred thirty four" - note that there is no "and" used in this case between the hundreds and tens.
Phone numbers are different and are almost always read digit-by-digit. I am guessing this is because they are very important numbers and/or security codes that could be misunderstood quite easily.
Relating to the first point, often you will hear people slow down and pronounce each individual digit for all cases if mistakes cannot be made or if a misunderstanding has already occurred. A conversation may go:
Grocer: The total is One hundred twenty three dollars and forty-five cents. Me: How much? One thirty two and forty five? Grocer: One Two three point four five. Me: Oh! Got it!
To answer the question, I will state that it depends on context. If exact numbers are crucial, stating individual numbers is fine and expected. If the numbers are ancillary or may not matter as much, then number groups or even fast estimates may be employed. instead.