Number()

new Number(value)
Number(value)

const a = new Number("123"); // a === 123  false
const b = Number("123"); // b === 123  true
a instanceof Number; //  true
b instanceof Number; //  false
typeof a; // "object"
typeof b; // "number"

+1n; // TypeError: Cannot convert a BigInt value to a number
0 + 1n; // TypeError: Cannot mix BigInt and other types, use explicit conversions

Number(1n); // 1

BigInt(Number(2n ** 54n + 1n)) === 2n ** 54n + 1n; // false