There is a grammatically correct way to write numbers in the English language.  When you write numbers or refer to numbers in your written text, you need to know whether you can use numeric figures or  words when you write a number.

10 rules to write numbers

When you write numbers, you need to keep the following in mind.
1. Whenever you write a lot of numbers, or a list of numbers, choose either words or numerals, and then stick with that format. for example:There were 2 lions, 3 elephants and 1 giraffe at the zoo.
2. If the numbers exceed 9, the rule is that you write the numerals, or figures. If the number is smaller than ten, you use the word for the number.  The pilot had flown 55 thousand miles.  There were four cars in the garage.
3. If the numbers are made up of two words, and it is under a hundred, hyphenate the two words.
She is twenty-one today
4. If one number follows another, but they are not related, spell one out as a word, the other as a number,
The landlord has 3 two-bedroomed apartments for rent
5. If you are starting a sentence with a number, you need to write out the number.
Twelves years later, Mary returned to the city.
6. Commas must be used when you have large numbers, such as $4,356.00
7. Exact mathematical figures and figures of measurement – decimals, fractions, page numbers, gallons, heights, etc  always appear as figures.
8. Write an address number as a figure, unless, as the rule about one figure following another applies, in which case you write one figure, and one word.
114 Second Street.
9. When you write dates as figures which is most of the time, you do not add the ‘nd’, ‘st’, ‘rd’, etc modifiers.
My flight is on Friday, June 2.
10. If you are writing percentages in a formal document, you can write them as words, otherwise use figures and the percentage sign.

When you write numbers or refer to numbers in your written text, you need to know whether you can use numeric figures or  words when you write a number. You would have seen many examples of how to write numbers in signage, magazines, online and so it is probably and area of English rules and usage that comes automatically to you.