Maths is universal!
There are many interesting facts out there. For example, Henry VIII had more wives than fingers on one hand. Cherophobia is the phobia of fun. And a flock of crows is called a murder.
They may seem (fairly) interesting to you and I, but if we were to meet extraterrestrial life, they wouldn't have a clue what we were talking about. Of course, how would they know what a crow is? Who could Henry VIII possibly be?
In fact, the only way could truly communicate with aliens is by using maths. And not maths using our decimal system - because they would not know what to make of our strange symbols. Instead we could show them that 1+1=2, indicated using objects.
This may seem laughably simple , but it shows them that we are indeed intelligent life, and not only that but we have a grasp of the universal language that is mathematics.
Having done this we could assign our regular decimal numbers to the numbers added together. However, this would only work up to ten; our decimal system only came into being because that is how many fingers we have in total. As a result, it is nearly impossible to show how our two-digit numbers would work, because there is no way to explain what two numbers next to each other means.
But it's a start.
And because frankly there is a lot of time between now and when we do meet intelligent extraterrestrial life who don't want to eat/kill us; hopefully we will be able to overcome this hurdle before, (if) the time comes.