# What is JavaScript’s highest integer value that a number can go to without losing precision?

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:

• 253-1, 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 253 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 231-1, 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.