What is the least common multiple of 23?
Short answer: There is none.
There is not a least common multiple of a single number, such as 23, because there cannot be any form of common multiple without two or more numbers to compare. Common multiples are multiples that the numbers being compared have in common. The least common multiple is the smallest multiple that all the numbers being compared have in common. Thus, since there are not two or more numbers to compare, there is not a least common multiple.
The least common multiple of two numbers is the product of the two numbers divided by their greatest common factor. The greatest common factor of 5 and 23 is 1. (See related question "What is the greatest common factor of 5 and 23?" for this calculation.) So, the least common multiple is 5 x 23 ÷ 1 = 115.