Number letter counts
If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.
NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of "and" when writing out numbers is in compliance with British usage.
The Puzzle
Denote the number of letters in the first n numbers as S(n), so that S(5) = 19. You might also care to verify that S(300) = 5,168 and S(3,000) = 85,946.
To find this geocache, calculate S(6785), and S(6840) ÷ 27.