In medieval Germanic counting, a thousand could mean 1200
Historians sometimes call 1000 a short thousand, to separate it from the Germanic long thousand of 1200 that turns up in medieval sources. Even today the word slips around: a kilogram is exactly a thousand grams, but in computing a kilo has often meant 1024.
Words for the number come from several languages. A group of a thousand things is occasionally a chiliad, from Ancient Greek, and a span of a thousand years can be a chiliad too, though millennium, from Latin, is far more common. Geologists and others borrow the SI prefix to write ka, for kiloannum, meaning a thousand years.
Everyday shorthand is just as varied. Replacing the last three zeros with K gives salaries like $30k, and Y2K named the computer problem expected in the year 2000. A thousand dollars or pounds is a grand, which Americans sometimes shorten to G. In print, English speakers may separate the digits with a comma, some others use a period, and the SI style recommends a non-breaking space.
As the first number with four digits, 1000 opens a stretch full of curiosities. The smallest four-digit prime comes just after it, at 1009, and there are 1061 primes between 1000 and 10000 in all, a count that is itself prime. The number 1060 is the total of the first twenty-five primes, the ones from 2 up to 97. And 1093 is the smallest Wieferich prime, a rare kind with a special property involving powers of 2.
Geometry and puzzles appear nearby as well. The number 1035 is the 45th triangular number, 1016 is how many points lie on the surface of a cube with edges 14 units long, and 1040 counts the pieces visible in a four-dimensional Rubik's tesseract measuring 6 along each side.
Source: 1000 (number)
