Personal Blogs
It started from their Jeep, with number plate 5021, which is considered as the most lucky vehicle that they have ever possessed. Not having an accident, better mileage, giving a predictable behavior, and not giving major maintenance work made it so. They gave credit to the last two digits of its number plate, 21. So now they assume that it is number 21 which makes the thing better.
When family business is in construction domain and when family is joint generally there are 10 bikes, 4 cars and 4/5 construction machines. Most of the personal vehicles have 5021 in RTO number or XX21. But this choice adds many restrictions sometimes. Like, many a time we have waited for many months until the number series is available.
This number choice doesn’t restricts to cars but then phones/mobile numbers and flight seat numbers or rounding transaction such that 21 is part of it.
But this bias about numbers grabs attention everything it appears anywhere.
Eg., I found this excellent book which explains Bitcoin so well and its named as 21 Lessons.
The number has some mathematical properties 21 Number has a special page on the wikipedia.
It mentions the number is Fibonacci, Triangular Number (1 + 2 + 3 + 4 + 5 + 6) and many more special properties.
BTW, both summer/winter solstices fall on 21st June and Dec respectively.
Finally, for crypto enthusiasts, the total number of Bitcoin to be released is 21 million.
The number 21 has also significance in Hindu scriptures and in the worship of Lord Ganesha.