We need to learn the sequence of wording the number system to write the numbers in words and this series will start from the extreme right digit.
Series: Ones, Ten, Hundred, Thousand, Ten Thousand, Lakhs.
Lets split the twelve thousand twelve hundred and twelve in digits
Twelve thousand is in thousands position = 1200
Twelve hundred is in hundred positions = 1200
Twelve is in tenth place 1 = 12
Add the three numbers
twelve thousand twelve hundred and twelve in digits is 13212.