In which language is 17 a swear word?

Commonly used as euphemisms are certain numerals, especially "sjutton" ('seventeen'; phonologically reminiscent of "satan" and "skit"), and variant form "tusan" from "tusen" ('thousand'; reminiscent of "satan")

There are several levels to cursing in Swedish, and the expressions seen as less naughty are those made up by numbers. In Sweden, bad words mostly have a religious origin and in the past it was common to amplify them with numbers, such as ‘sjutton’ (17), ‘attans’ (an old word for 18), and ‘tusan’ (meaning 1,000). All the little devils and other bad things coming after those numerals have vanished over time, and the measurements are all that is left.