### Number Notation

Hierarchy of Decimal Numbers
 Number Name How many 0 zero 1 one 2 two 3 three 4 four 5 five 6 six 7 seven 8 eight 9 nine 10 ten 20 twenty two tens 30 thirty three tens 40 forty four tens 50 fifty five tens 60 sixty six tens 70 seventy seven tens 80 eighty eight tens 90 ninety nine tens

 Number Name How Many 100 one hundred ten tens 1,000 one thousand ten hundreds 10,000 ten thousand ten thousands 100,000 one hundred thousand one hundred thousands 1,000,000 one million one thousand thousands
Some people use a comma to mark every 3 digits. It just keeps track of the digits and makes the numbers easier to read.
Beyond a million, the names of the numbers differ depending where you live. The places are grouped by thousands in America and France, by the millions in Great Britain and Germany.
 Name American-French English-German million 1,000,000 1,000,000 billion 1,000,000,000 (a thousand millions) 1,000,000,000,000 (a million millions) trillion 1 with 12 zeros 1 with 18 zeros quadrillion 1 with 15 zeros 1 with 24 zeros quintillion 1 with 18 zeros 1 with 30 zeros sextillion 1 with 21 zeros 1 with 36 zeros septillion 1 with 24 zeros 1 with 42 zeros octillion 1 with 27 zeros 1 with 48 zeros googol 1 with 100 zeros googolplex 1 with a googol of zeros
FractionsDigits to the right of the decimal point represent the fractional part of the decimal number. Each place value has a value that is one tenth the value to the immediate left of it.
 Number Name Fraction .1 tenth 1/10 .01 hundredth 1/100 .001 thousandth 1/1000 .0001 ten thousandth 1/10000 .00001 hundred thousandth 1/100000
Examples:
0.234 = 234/1000 (said - point 2 3 4, or 234 thousandths, or two hundred thirty four thousandths)
4.83 = 4 83/100 (said - 4 point 8 3, or 4 and 83 hundredths)
SI Prefixes
 Number Prefix Symbol 10 1 deka- da 10 2 hecto- h 10 3 kilo- k 10 6 mega- M 10 9 giga- G 10 12 tera- T 10 15 peta- P 10 18 exa- E 10 21 zeta- Z 10 24 yotta- Y
 Number Prefix Symbol 10 -1 deci- d 10 -2 centi- c 10 -3 milli- m 10 -6 micro- u (greek mu) 10 -9 nano- n 10 -12 pico- p 10 -15 femto- f 10 -18 atto- a 10 -21 zepto- z 10 -24 yocto- y

Roman Numerals
 I=1 (I with a bar is not used) V=5 _ V=5,000 X=10 _ X=10,000 L=50 _ L=50,000 C=100 _ C = 100 000 D=500 _ D=500,000 M=1,000 _ M=1,000,000
 ```1 = I 2 = II 3 = III 4 = IV 5 = V 6 = VI 7 = VII 8 = VIII 9 = IX 10 = X``` ```11 = XI 12 = XII 13 = XIII 14 = XIV 15 = XV 16 = XVI 17 = XVII 18 = XVIII 19 = XIX 20 = XX 21 = XXI``` ```25 = XXV 30 = XXX 40 = XL 49 = XLIX 50 = L 51 = LI 60 = LX 70 = LXX 80 = LXXX 90 = XC 99 = XCIX ```
There is no zero in the roman numeral system.
The numbers are built starting from the largest number on the left, and adding smaller numbers to the right. All the numerals are then added together.
The exception is the subtracted numerals, if a numeral is before a larger numeral, you subtract the first numeral from the second. That is, IX is 10 - 1= 9.
This only works for one small numeral before one larger numeral - for example, IIX is not 8, it is not a recognized roman numeral.
There is no place value in this system - the number III is 3, not 111.
Number Base Systems
 Decimal(10) Binary(2) Ternary(3) Octal(8) Hexadecimal(16) 0 0 0 0 0 1 1 1 1 1 2 10 2 2 2 3 11 10 3 3 4 100 11 4 4 5 101 12 5 5 6 110 20 6 6 7 111 21 7 7 8 1000 22 10 8 9 1001 100 11 9 10 1010 101 12 A 11 1011 102 13 B 12 1100 110 14 C 13 1101 111 15 D 14 1110 112 16 E 15 1111 120 17 F 16 10000 121 20 10 17 10001 122 21 11 18 10010 200 22 12 19 10011 201 23 13 20 10100 202 24 14
Each digit can only count up to the value of one less than the base. In hexadecimal, the letters A - F are used to represent the digits 10 - 15, so they would only use one character.

Courtesy : http://systempost.blogspot.in