I'm learning number, big numbers like one hundred (100) or one thousand (1000).

The question is: for a *composed* number e.g. 73,987, that I can write as,  
*seventy-three thousand, nine hundred **and** eighty-seven*

Is the **and** word mandatory?  
or can I simply write *seventy-three thousand, nine hundred eighty-seven*

another example: 123,601,  
*one hundred twenty-three thousand, six hundred one*  
*one hundred **and** twenty-three thousand, six hundred **and** one*

And if there are differences between British and American English.