123; // one hundred and twenty three
123.0; // same number
123 === 123.0; // true
123 + 123; // 246
123 + "123"; // "123123"
"100" - "10"; // 90;
"100" + "10"; // "10010";
NaN // Not a Legal Number

function expo(x, f) {
return Number.parseFloat(x).toExponential(f);
}
  
console.log(expo(123456, 2)); // Expected output: "1.23e+5" 

const numObj = new Number(42);
typeof numObj; // Expected output: "object"
numObj.valueOf(); // Expected output: 42

Number.isInteger("123"); // false

num.toString()  // to turn a number into a string
num.toExponential()  // returns a number in exponential notation
toFixed()     // returns a number, written with a specified number of decimals (currency) toFixed(2)  
toPrecision()   // returns a number with a specified length, ex: 9.567.toPrecision(2) = 9.6
valueOf()     // returns a number as a number 
        
Number()    // can be used to convert variables into numbers. Turns Dates into milliseconds.
+variable //  Unary plus (+) converts operands into numbers. Good for strict comparisons. 
parseInt()   // parses a string and returns a whole number 
parseFloat()   // parses a string and returns a number
isNaN(num) //  determines whether a value is not a number 
isInteger()   // returns true if argument is an integer
isSafeInteger() // returns true if argument is a safe integer

2.3345.toFixed(2); // 2.33

parseInt("   60   "); // returns number 60

Number.isSafeInteger(123); // true
Number.isSafeInteger(0.5); // false

const num = 10;
num.toString(); // "10"

2.3345.toPrecision(2); // 2.3

Number("123"); // returns the number 123

parseFloat("  60  "); // 60