Skip to main content
2 of 2
replaced http://math.stackexchange.com/ with https://math.stackexchange.com/

In the ordering $\preceq$ of nonnegative integers by divisibility, 1 is the least element and 0 is the greatest, and we have for instance $$ 1\preceq 2\preceq 6\preceq 12\preceq\dots\preceq 0.$$ In this ordering, gcd is the same as meet (greatest lower bound), which is dual to least upper bound, which is what boolean OR is for $\{0,1\}$.

So it makes sense if you think of numbers as "degrees of truth", where multiplicative factors are evidence of falsehood.

See also: What is gcd(0,0)?

Bjørn Kjos-Hanssen
  • 24.8k
  • 3
  • 58
  • 114