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## What’s special about the number 21?

2 21 is a triangle number – it is the sum of the first six whole numbers (1+2+3+4+5+6=21). 3 21 is the eighth number in the Fibonacci sequence, where each number is the sum of the two preceding ones. 4 A shape with 21 sides is called a icosikaihenagon. 5 21 is the atomic number of the chemical element scandium.

## Why is 25 a special number?

In mathematics It is a square number, being 5^{2} = 5 × 5. It is the smallest square that is also a sum of two (non-zero) squares: 25 = 3^{2} + 4^{2}. Hence it often appears in illustrations of the Pythagorean theorem. 25 is the sum of the five consecutive single-digit odd natural numbers 1, 3, 5, 7 and 9.

## What’s special about the number 20?

20 is a tetrahedral number as 1, 4, 10, 20. 20 is the basis for vigesimal number systems. 20 is the third composite number to be the product of a squared prime and a prime, and also the second member of the (2^{2})q family in this form. 20 is the smallest primitive abundant number.

## Is 5 a lucky number?

People with the lucky number 5 usually tend to pursue freedom. In general, people with this lucky number are free, adventurous and energetic. Sometimes, they are full of a sense of curiosity and contradiction.

## Which is the best number in the world?

And the World’s Favorite Number Is A survey launched by a British mathematics writer has found that seven is the world’s favorite number, reports The Guardian. The results of the online survey were published on Tuesday, with three, eight and and four coming second, third and fourth.

## Who invented 24-hour time?

Our 24-hour day comes from the ancient Egyptians who divided day-time into 10 hours they measured with devices such as shadow clocks, and added a twilight hour at the beginning and another one at the end of the day-time, says Lomb.

## What’s the meaning of 11 11?

In numerology, some New Age believers often link 11:11 to chance or coincidence. It is an example of synchronicity. For instance, those who are seeing 11:11 on a clock often claim it as an auspicious sign or signaling a spirit presence.

## Whats does AM and PM mean?

In decimal, it is the first composite number not divisible by any of its digits. It is the radix (base) of the septemvigesimal positional numeral system. 27 is the only positive integer that is 3 times the sum of its digits. In a prime reciprocal magic square of the multiples of 17, the magic constant is 27.

## Why is 28 a special number?

In mathematics Twenty-eight is the second perfect number – it’s the sum of its divisors: 1+2+4+7+14. As a perfect number, it is related to the Mersenne prime 7, since 2(2^{3} − 1) = 28. It is also a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 2, 8, 10, 18, 28