Here, we will not only tell you what the sum of integers from 1 to 645 is, but also show you how to calculate it fast. The sum of the integers from 1 to 645 is 208,335.
To get the answer above, you could add up all the digits like 1+2+3... +645, but there is a much easier way to do it! Use the following formula:
n(n + 1)/2 = Sum of Integers
In this case, n=645, thus you get your answer by entering 645 in the formula like this:
645(645 + 1)/2 = 208,335
Sum of Integers Calculator
To get the sum of integers from 1 up to another number, please enter that other number here: