This is true for 1 and 2 also. The symbol for 7 looks like an upside down 7 (七). 5 can be highlighted in the symbol (五)
The pronunciations are different, but these are the same numerals used in Japanese.
That's probably why it is written as such as well, Chinese characters all have stories behind them. :)
We just learned how to read symbols. But i dont know what is 1 to 10 in chinese