You cannot find the LCM of only one number, two or more are needed.
It is not possible to give a sensible answer to this question. The least common multiple (LCM) refers to a multiple that is COMMON to two or more numbers. You have only one number in the question!
As presented in the question it looks like a single number 51015. The lowest common multiple of 51015 depends upon the other number(s) with which 51015 has common multiples, but it will always be one of the multiples of 51015, namely: 51015, 102030, 153045, 204060, 255075, 306090, ... However, I suspect that you wrote the question separating 5 10 and 15 by commas with no spaces following the commas (ie ``...multiple of 5,10,15'') - unfortunately due to limitations some punctuation (the comma being one of them) get stripped from questions. The lowest common multiple of 5, 10 and 15 is 30.