The obsession of numbers is not a good one. As an architect, it is well known that in order to govern all the numbers in a design, something called a "module" is adopted which is basically an old-school gridiron of multiplications of 60. I would say the module is not dead, far from it, but a typical architect's application of it is so dead, I would say as dead as the aesthetics of the mustache. The number 3 (three, trois, tres, ثلاثة) is one of those outstanding things out there. the combination of three, six, and nine is for some reason is magnetic to think of. For example, the number nine when halved is 4.5, and when you add those numbers together they're 9 again (4.5: 4+5=9). Nine as a unit, multiplied by two equals 18, also added together they're nine (18: 1+8=9). Multiplied by three equals 27 (27: 2+7=9) and so on with 36, 45, 54, 63,... That is outrageously beautiful! 99, the total number of praise names of God in Islam, is also nine (99: 9+9=18, 1+8=9). At increments of three, the meeting point of those numbers is also fabulous, at any given increment, two of those three numbers are at play. For example 30 can be divided by 3 and 6, but not by 9. Going down one increment is 27, which can be divided by 3 and 9, but not by six. The next would be 24, dividable by 3 and 6, but not by 9. 21 is an anomaly, it is only dividable by 3 (and 7), as is 15 which is only dividable by 3 (and 5). It is a never-ending spiral that will result in one's madness.
4 is not as interesting, to me, but I can't ignore how it compliments 3. 4 multiplied by 6 which is 3x2 is 24 which is also 6 (24: 2+4=6). 3 x 4 is 12 which is 3 (12: 1+2=3). 3/4 = 0.75 (7+5=12, 1+2=3). 2x2=4, 3x2=6, 46 is the chromosome count in our DNA, 46/2=23. 2+3+4=9. 3 is the fourth number in the Fibonacci numbers.
It all sounds like an arbitrary selection of numbers and what they do together, but its enough to make one's hair stand for a minute.