Why is Number.MAX_SAFE_INTEGER 9,007,199,254,740,991 and not 9,007,199,254,740,992?

Question

ECMAScript 6\'s Number.MAX_SAFE_INTEGER supposedly represents the maximum numerical value JavaScript can store before issues arise with floating point precision

Answer 1

the only number which is in close proximity of another when compared with its next number shows true

9007199254740992 == 9007199254740993
true
9007199254740993 == 9007199254740994
false
9007199254740991 == 9007199254740992
false
9007199254740997 == 9007199254740998
false