good ones! as an english speaker, some things that gave me difficulty in a second language (see if you can guess it):
- some digits are pronounced differently for counting than as part of a larger number
- some digits are pronounced differently when reciting the individual digits of a number, like in a phone number
- phrasing like "one hundred 2" means 120, not 102
- large numbers not grouped in thousands, but in ten thousands, ie having a single word for 10000, a word for 10^7, etc, so a valid spoken number is "13 thousand ten-thousand" -> 1.3 billion
- some digits are pronounced differently for counting than as part of a larger number - some digits are pronounced differently when reciting the individual digits of a number, like in a phone number - phrasing like "one hundred 2" means 120, not 102 - large numbers not grouped in thousands, but in ten thousands, ie having a single word for 10000, a word for 10^7, etc, so a valid spoken number is "13 thousand ten-thousand" -> 1.3 billion