Which is the most common symbol or abbreviation for the word "number"?

I'm fully aware of the numero sign (it's the default way in my language), but in English I have seen the numero sign, number sign, the no, num and numb. abbreviations and so on.

For example, the ways used in English are not common in Spanish, Italian or Portuguese. Many people in these countries wouldn't even recognize the # sign as an abbreviation for number since numero is the most common way.

So my question is: is there a sign for number that is globally recognized? And if so: what to do about plurals?