💡 Số đếm — Fun Facts

The number shapes we use, like 1, 2, 3, first came from India.

Long ago, clever people in India wrote numbers this way. The shapes traveled around the world, and now almost everyone uses them.

A 'million' is a 1 followed by six zeros.

A million is a thousand thousands — a really enormous pile! If you tried to count to a million, it would take you many days.

The number after 9 is 10, our first two-digit number.

Once you count past 9, you need two digits. 10 is written with a 1 and a 0 standing side by side.

Zero is the number that means 'none'.

Zero stands for having nothing at all. It may seem small, but it is a very important and useful number.

We write every number using just ten digits, 0 through 9.

Even a huge number is built from these ten little digits. We just mix and match them in different spots.

Counting numbers go on forever — you can always add one more.

No matter how big a number is, you can always say a bigger one by adding one. There is no biggest counting number!

Numbers help us tell how many things there are.

Whenever you say how old you are or how many cookies you have, you are using numbers. They are everywhere!

A “googol” is the number 1 followed by 100 zeros.

It’s bigger than the number of atoms in the part of the universe we can see. The search engine Google is named after it, with a spelling twist.

A 'googolplex' is an even bigger number — a 1 followed by a googol of zeros.

A googolplex is so enormous that you could never write out all its zeros. There isn't enough room in the entire universe to print them, even in the tiniest possible writing.

A 'dozen' means 12, and a 'baker's dozen' means 13.

Long ago, bakers added an extra loaf to every dozen so they wouldn't get in trouble for accidentally selling bread that was a bit too small or light. Thirteen-for-twelve became known as a baker's dozen.

Any number multiplied by zero is always zero.

Multiplying is like adding a number that many times. Multiplying by zero means adding it no times at all — so you're left with nothing, which is zero.

In a room of just 23 people, it's more likely than not that two share a birthday.

It feels surprising, but you're comparing every possible pair of people, not just yourself against the others. With 23 people there are 253 possible pairs, which tips it over 50%. This is called the 'birthday paradox'.

The word 'four' is spelled with four letters — the only number in English like that.

F-O-U-R has exactly four letters, matching its own value. No other English number word matches its number, which makes 'four' a fun one-of-a-kind.

If you could fold a piece of paper 42 times, it would reach all the way to the Moon.

Each fold doubles the thickness, and doubling grows unbelievably fast. After 42 folds the paper would be about 400,000 km thick. In real life, though, paper can only be folded a handful of times.

Zero is the only number that can't be written with Roman numerals.

Romans wrote numbers using letters like I, V, X, and M, but they had no symbol for zero at all. The idea of zero as its own number reached Europe later, from Indian and Arabic mathematics.

A 'googol' is a 1 followed by one hundred zeros.

That's a mind-bogglingly big number — even bigger than the number of atoms we think are in the whole visible universe. The company Google was named after it, with a little spelling twist.

The Romans had no symbol for zero.

Roman numerals like I, V, X and C have no zero at all. The idea of zero as a number reached Europe much later, from Indian and Arabic mathematics.