0 is not a natural number . What exists in 0 ? What physically exists in 0 ?

Bullshit.

https://www.newworldencyclopedia.org/entry/0_(number)
0 (zero) is both a

number and a numerical digit used to represent that number in numerals. As a number, zero means

*nothing*—an absence of other values. It plays a central role in mathematics as the identity element of the

integers, real numbers, and many other algebraic structures. As a digit, zero is used as a placeholder in place value systems. Historically, it was the last digit to come into use. In the

English language, zero may also be called nil when a number, o/oh when a numeral, and nought/naught in either context.

**0 as a number**
0 is the

integer that precedes the positive

1, and follows −1. In most (if not all) numerical systems, 0 was identified before the idea of 'negative integers' was accepted.

Zero is an integer which quantifies a count or an amount of null size; that is, if the number of your brothers is zero, that means the same thing as having no brothers, and if something has a weight of zero, it has no weight. If the difference between the number of pieces in two piles is zero, it means the two piles have an equal number of pieces. Before counting starts, the result can be assumed to be zero; that is the number of items counted before you count the first item and counting the first item brings the result to one. And if there are no items to be counted, zero remains the final result.

While mathematicians all accept zero as a number, some non-mathematicians would say that zero is not a number, arguing one cannot have zero of something. Others hold that if you have a bank balance of zero, you have a specific quantity of money in your account, namely none. It is that latter view which is accepted by mathematicians and most others.

Almost all historians omit the year zero from the proleptic Gregorian and Julian calendars, but astronomers include it in these same calendars. However, the phrase Year Zero may be used to describe any event considered so significant that it virtually starts a new time reckoning.

**0 as a numeral**
The modern numeral 0 is normally written as a circle or (rounded) rectangle. In old-style fonts with text figures, 0 is usually the same height as a lowercase On the seven-segment displays of calculators, watches, etc., 0 is usually written with six line segments, though on some historical calculator models it was written with four line segments. This variant glyph has not caught on.

It is important to distinguish the

*number* zero (as in the "zero brothers" example above) from the

*numeral* or

*digit* zero, used in numeral systems using positional notation. Successive positions of digits have higher values, so the digit zero is used to skip a position and give appropriate value to the preceding and following digits. A zero digit is not always necessary in a positional number system: bijective numeration provides a possible counterexample.