I believe you meant an arithmetic series. It is a series of numbers differing by a certain number from the previous number of the series. In this case, they differ by 123.
The result of adding two numbers is their sum.
The sum of 123 is 123.
sum
The sum.
The sum. the sum of
A sum.
The sum.
Adding two or more numbers together gives you a sum.
7272 * * * * * WRONG! Sum from 23 to 123 = (sum from 1 to 123) minus (sum from 1 to 22) = 123*124/2 - 22*23/2 = 7626 - 253 = 7373. NOT 7272!
The sum of 123 and 2,223,223 is 2,223,346
Addend plus addend equals sum.
If you are adding, the result is a sum. This terminology applies whether the addends (the terms you are adding) are whole numbers or they are expressed as fractions or in decimal notation. The same is true of the sum.