JavaScript has two number types: `Number`

and `BigInt`

.

The most frequently-used number type, `Number`

, is a 64-bit floating point IEEE 754 number.

The largest exact integral value of this type is `Number.MAX_SAFE_INTEGER`

, which is:

- 2
^{53}-1, or - +/- 9,007,199,254,740,991, or
- nine quadrillion seven trillion one hundred ninety-nine billion two hundred fifty-four million seven hundred forty thousand nine hundred ninety-one

To put this in perspective: one quadrillion bytes is a petabyte (or one thousand terabytes).

“Safe” in this context refers to the ability to represent integers exactly and to correctly compare them.

From the spec:

Note that all the positive and negative integers whose magnitude is no

greater than 2^{53}are representable in the`Number`

type (indeed, the

integer 0 has two representations, +0 and -0).

To safely use integers larger than this, you need to use `BigInt`

, which has no upper bound.

Note that the bitwise operators and shift operators operate on 32-bit integers, so in that case, the max safe integer is 2^{31}-1, or 2,147,483,647.

```
const log = console.log
var x = 9007199254740992
var y = -x
log(x == x + 1) // true !
log(y == y - 1) // also true !
// Arithmetic operators work, but bitwise/shifts only operate on int32:
log(x / 2) // 4503599627370496
log(x >> 1) // 0
log(x | 1) // 1
```

Technical note on the subject of the number 9,007,199,254,740,992: There is an exact IEEE-754 representation of this value, and you can assign and read this value from a variable, so for *very carefully* chosen applications in the domain of integers less than or equal to this value, you could treat this as a maximum value.

In the general case, you must treat this IEEE-754 value as inexact, because it is ambiguous whether it is encoding the logical value 9,007,199,254,740,992 or 9,007,199,254,740,993.