There may be some significance (symbolic) to numbers or it is just a superstition or coveted or lucky numbers:
0 Just as indefinable as God
1 There is only One God!
3 Holy Trinity, Three musketeers, & Three times is a charm.
5 The Sacred Five-AhlalBait
6 The universe was created in Six days, To Ismailis, that is where the name comes from Mawlana Ismail (Imam Ismail)
7 Seven days in a week (Satarada? Don’t now how to spell), also multiples of 7, 21, 28…
9 Nine, as the highest single-digit number, symbolizes completeness.
10 The ten reincarnations Das-Avtar (hindu-khoja belifes)
11 It has been given some significance but I don’t know a lot besides it the Imamet Day (July 11th) there are also multiples of 11,33,99…
12 A dozen roses, 12 inches to a foot, 12 hours = Half a Day, also significant to the twelvers, although, in some cultures (Russian and some central Asian) 12 is unlucky and they give bakers’ dozen (12+1)
13 Is considered lucky in some circles, To Ismailis it has two significance but one is as commonly celebrated is the Present Imam’s Birthday and the second one is the continuations of Imamet via Mawlana Mansoor (Imam Al-Mansoor) And in some cultures 13 is unlucky and in many places even skipped! i.e. some building floors will skip form 12 to 14.
21 The obvious one would be NovRose (March 21st) but there are some other things that do go on in world that is related to 3 week or 21 days, one of which is related to fertility a good example would be chicken lay eggs for 21 days. There is also similar relationship with humans where women’s fertility is concerned.
28&29 completes a lunar month and menstrual month.
33 This is something not very clear on but people do recite repetitive name(s) in that order some thing along the line of Tasbi
51 Is very little known about it and much of it Persian mystery and also known as the time when the 51st Imam declares his divinity (the Imam’s name or title supposes to be Quiam). Ok sports fans, in my very recent quest to find what’s all the buzz about AbuAli, I stumbled onto 1979 lecture of his in Canada, where he had also found (researched) and conclude the same and further he estimated 129 years from 1979 for this to occur.
99 Are the names given to Allah’s attributes, also recite repetitive name(s) in that order some thing along the line of Tasbi
101 Is also given importance but I am not clear on it.
1001 Is also a fantasy One Thousand and One Nights Stories Arabian-Persian legends and myths and beliefs (just pick a Disney Movie)