Answer by BSalita for Why do I need 17 significant digits (and not 16) to represent a double?

The largest continuous range of integers that can be exactly represented by a double (8-byte IEEE) is -2⁵³ to 2⁵³ (-9007199254740992. to 9007199254740992.). The numbers -2⁵³-1 and 2⁵³+1 cannot be exactly represented by a double.

Therefore, no more than 16 significant decimal digits to the left of the decimal point will exactly represent a double in the continuous range.