The least common multiple of 58 and 81 is 4698. To find the least common multiple of big numbers, take 1/(number 1)+1/(number 2), then find a common denominator, then add them together and reduce. The denominator of this reduced fraction is the least common multiple. In this example, 1/58+1/81=81/4698+58/4698=139/4698, which does not reduce so 4698 is the least common multiple.