The value 1 billion regardless of whether it is 1 billion in the US, UK or Canada is always: 1,000,000,000
In the US and for most uses in the UK, the number of zeros is 18 (eighteen). 1,000,000,000 x 1,000,000,000 = 1,000,000,000,000,000,000 The name for a "billion billion" is a quintillion, 1 x 1018....
There are nine zeros in a billion and twelve in a trillion.
6.6 billion = 6,600,000,000 So there are 8 zeros
Either 9 or 12, depending on the definition. In English-speaking countries, usually 9.