I am -0 (or more negative) for the same reason. The need for lcm is very rare. I think the gcd doc should give the lcm formula, with perhaps an index entry. The gcd doc might also mention that gcd is associative: gcd(a,b,c) = gcd(gcd(a,b),c).

The math module is nearly all float math. The integer only math.factorial(n) is relatively recent. Gcd in in fractions because we do not have an imath module and because the only use of gcd in the stdlib is for reducing fractions.