Num lock. The Num Lock key exists because earlier 84-key IBM PC keyboards did not have cursor control or arrows separate from the numeric keypad. Most earlier computer keyboards had separate number keys and cursor control keys; however, to reduce cost, IBM chose to combine the two in their early PC keyboards.
The most common rule. The most common and frequently used rule for writing numbers in APA style is determined by whether the number is under 10. All those numbers should be written out in word form, such as four or seven. A number 10 and above is written as a numeral, such as 10, 17, 233.
The below diagram will help us to get the better concept on facts about reading and writing large numbers. So, while reading or writing a large number we need to start from the left side with the largest group and move to the right side. Reading and writing large numbers in words in thousand and hundred: