0 & 4 & 6
Well, according to that article, four is definitely a problem. Six, however, would appear to be a number to try to find instead of avoiding.
Lucky numbers are based on Chinese words that sound similar to other Chinese words. The numbers 6, 8, and 9 are believed to have auspicious meanings because their names sound similar to words that have positive meanings.
aus·pi·cious (adjective)
1. promising success; propitious; opportune; favorable: an auspicious occasion.
2. favored by fortune; prosperous; fortunate.
Four
Although the number 4 is considered unlucky by most Chinese (see Unlucky section for details), it is considered lucky in some regions of China where it is homonymous in the local dialect to the word "事(job, business, or task)". When the number 4 is encountered during a celebration, people would often remark "四四如意", which would also refer to "事事如意" (Everything done as wished).
4 also sounds like the word "思 (thinking)". 4 in solfège sounds like fa 发 meaning "get fortune; 14 in solfège sounds like "dou fa 都发 meaning "everyone gets fortunes".
Six
The number 6, pronounced liu, sounds like the word for "flowing", "smooth" or "slippery" which can mean "everything goes smoothly".
The number 666 can be seen prominently in many shop windows across the country, and people there often pay extra to get a mobile phone number including this string of digits.
Coincidentally, that number is considered to be demonic in Western culture, as it is the Number of the Beast. Unless you are an atheist like me and then it doesn't mean much of anything.
I am not trying to cause a dispute or anything. I am just questioning why?
Is there any other reason why "6" is not a premium number. I still have the question: who determines what is premium and what is not? Is there just very few sales with NNNN that include the number "6"? Is anybody keeping track of these type of sales?