In ActionScript 3.0, the Number data type can represent integers, unsigned integers, and floating point numbers. However, to maximize performance, you should use the Number data type only for integer values larger than the 32-bit int and uint types can store or for floating point numbers. To store a floating point number, include a decimal point in the number. If you omit a decimal point, the number will be stored as an integer.
The Number data type uses the 64-bit double-precision format as specified by the IEEE Standard for Binary Floating-Point Arithmetic (IEEE-754). This standard dictates how floating point numbers are stored using the 64 available bits. One bit is used to designate whether the number is positive or negative. Eleven bits are used for the exponent, which is stored as base 2. The remaining fifty two bits are used to store the significand (also called the mantissa), which is the number that is raised to the power indicated by the exponent.
By using some of its bits to store an exponent, the Number data type can store floating point numbers significantly larger than if it used all of its bits for the significand. For example, if the Number data type used all 64 bits to store the significand, it could store a number as large as 264. By using 11 bits to store an exponent, the Number data type can raise its significand to a power of 21023.
The maximum and minimum values that the Number type can represent is stored in static properties of the Number class called Number.MAX_VALUE and Number.MIN_VALUE.
Number.MAX_VALUE == 1.79769313486231e+308
Number.MIN_VALUE == 4.940656458412467e-324
Although this range of numbers is enormous, the cost of this range is precision. The Number data type uses 52 bits to store the significand, so numbers that require more than 52 bits to represent precisely, such as the fraction 1/3, are only approximations. If your application requires absolute precision with decimal numbers, you need to use software that implements decimal floating point arithmetic as opposed to binary floating point arithmetic.
When you store integer values with the Number data type, only the 52 bits of the significand are used. The Number data type uses these 52 bits and a special hidden bit to represent integers from -9,007,199,254,740,992 (-253) to 9,007,199,254,740,992 (253).
Flash Player uses the NaN value not only as the default value for variables of type Number, but also as the result of any operation that should return a number but does not. For example, if you attempt to calculate the square root of a negative number, the result will be NaN. Other special Number values include positive infinity and negative infinity.
NOTE The result of division by 0 is only NaN if the divisor is also 0. Division by 0 produces infinity when the dividend is positive or -infinity when the dividend is negative.