I'm confused about numbers written like this: 1091.45万, 51.5万 etc... Do I have to say 点 or just read the Chinese equivalent as 一千零九十一万四千五百 and so on? -------------------
1091.45万, the common out-reading way is ‘一千零九十一点四五万’
FYI：Chinese read integral numbers in 个ones, 十 tens, 百 hundreds, 千thousands, 万 （ten thousands）, and so forth.
When the number has a decimal, you read the integral part and then read' dian ' and the digits one after another. If the integral part is zero, the the number reads as ' 零点 digit2, digit 2, digit 3...
Note that when the munber is bigger than ten thousand, the basic reading unit is 万（not 千 thousand, as in English ）.1111 1111 reads as 一千一百（一）十一 万 一千一百（一）十一， 万万 is 亿，then 十亿, 百亿, 千亿，万亿.
Numbers bigger than 万亿 usually do not read in the above units. You may read them in every 4/3/2 digits to others (in the same way as you read phone numbers).