# True or False: Math.pow(2, 53) == Math.pow(2, 53) + 1 ?

### Adrian twitter logo Mar 31・1 min read

Hello code newbies:

I have a fun JavaScript question for you.

Is the following expression `True` or `False`?

``````Math.pow(2, 53) == Math.pow(2, 53) + 1
``````

Explain!

DISCUSS (6)
Discussion At first, I was confused why this would not return `false`, but of course you wouldn't have posted this if it would return `false`. 😃

While looking into why these statements are evaluated to be equal, I stumbled upon an even more interesting problem: When you try to enter exceedingly big numbers into a JavaScript console, they will be returned similiarly but not with the exact same value. For example, `9007199254740992111` will be transformed into `9007199254740992000`. This sounded awfully like floating point issues. After having a look, the way integers are stored in JavaScript engines using 64 bits, which means there's a limit to correctly display numbers above a certain threshold. And that threshold appears to be 2^53, which explains why you took those parameters for `Math.pow`!

Previously, I was only aware of examples where floating point issues arise with the storage of numbers smaller than zero, leading me to think it would be a "comma problem" (for example `0.1 + 0.2 != 0.3`), but this example made clear for me that this of course can also happen for big numbers.

This thread helped me understand the details, it's worth checking out.

Actually, `Math.pow(2, 53) === Math.pow(2, 53) + 1` (triple equals), unless your wrap in BigInt.

Every programming languages have a concept of `Number.MAX_SAFE_INTEGER`.

Yeah, Python doesn't tell you about `short`, `long`, `float` and `double` and it automates this; but for JavaScript, it is always `double`.

I am actually stumbled in standard Python that it is `False`, instead of throwing an error. It will not be the case in Kotlin.

``````>>> 2 ** 64 == 2 ** 64 + 1
False
>>> type(2 ** 64 + 1)
<class 'int'>
``````

Now, I can ask on StackOverflow, but SO is such as scary place. There is this in Quora, but not many wants to answer.

It seems that it is bignum, actually. You don't even have to care about Decimal, unless you care about `0.1 + 0.2`

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