Everyone starts with these one digit numbers:

number	cardinal number	ordinal number
0	zero	.
1	one	first
2	two	second
3	three	third
4	four	fourth
5	five	fifth
6	six	sixth
7	seven	seventh
8	eight	eighth
9	nine	ninth

Then, we learn the 'teens':

number	cardinal number	ordinal number
10	ten	tenth
11	eleven	eleventh
12	twelve	twelfth
13	thirteen	thirteenth
14	fourteen	fourteenth
15	fifteen	fifteenth
16	sixteen	sixteenth
17	seventeen	seventeenth
18	eighteen	eighteenth
19	nineteen	nineteenth

After that, the tens:

number	cardinal number	ordinal number
20	twenty	twentieth
30	thirty	thirtieth
40	forty	fortieth
50	fifty	fiftieth
60	sixty	sixtieth
70	seventy	seventieth
80	eighty	eightieth
90	ninety	ninetieth

And finally, the common 'big numbers' :

number	cardinal number	ordinal number
100	hundred	hundredth
1,000	thousand	thousandth
10,000	ten thousand	ten thousandth
100,000	hundred thousand	hundred thousandth
1,000,000	million	millionth
10,000,000	ten million	ten millionth
100,000,000	hundred million	hundred millionth
1,000,000,000	thousand million (or milliard)	thousand millionth

Scientists (and trivia buffs) might be interested in this list of Œreally big numbersı :

number	cardinal number
10E12	billion
10E15	1,000 billion
10E18	trillion
10E21	1,000 trillion
10E24	quadrillion
10E27	1,000 quadrillion
10E30	quintillion
10E33	1,000 quintillion

What's next (all are short introductions to these topics, useful for English Language learners and young native speakers) :