Number formats
In all numbers over three digits, at least one comma will be required. Counting from right to left, place a comma after every third number. It is important to note that this is different from many European countries, where the comma and period have reverse roles.
Ex

3,000 
450,000  
30,000,000 
To create the abbreviated version of an ordinal number, write the numeral form followed by the last two letters of the word.
Ex

First à 1 + st = 1^{st} 
Second à 2 + nd = 2^{nd}  
Third à 3 + rd = 3^{rd}  
Fourth à 4 + th = 4^{th} 
 Here are some simple rules to keep in mind about when to write out numbers. All numbers under 10 should be written out, as well as any number at the beginning of a sentence. Fractions can be written out as well (and usually require a hyphen).
Ex

Eighty people boarded a plane to Amsterdam last night. 
My daughter will be four next week.  
Onethird of the earth’s population cannot see the Milky Way due to pollution. 
 Numbers should be written as numeral for any numbers 10 and above, as well as dates and years. Percentages, decimals, and weights should also stay in numeral form. Finally, lists of numbers will be easier to read when in numeral form.
Ex

Approximately 60% of the student body voted for Kathleen. 
I worked 45 hours last week.  
Liam has three brothers aged 4, 7, and 15.  
à NOT: Liam has three brothers aged four, seven, and 15. 
 Note that numbers written out should include a hyphen between each individual number.
Ex

Eightytwo 
Thirtyfive 