Answer:
Symbols (Kanji), as long as not repetitious are as follows. For numbers not mentioned, a combination of these kanji is used. For instance, for 20 we use symbols of two and ten in order: 二十 /ni juu/ would be 20 and for twelve we use ten first and then two: 十二 /juu ni/ would be 12.
There is a difference in Japanese numeral values higher than '1,000'. They have one more step which is '10,000' and from then the multiplier unit to change the value level becomes 10,000, not 1000 like in English. Meaning the name of the numeral groups changes by 10^4 steps. Here there will be only as far as 10^20 (100 x quintillion), further than trillion (兆 /chou/) is hardly ever used and obscure.
零 /rei/ : zero
一 /i chi/ : one
二 /ni/ : two
三 /san/ : three
四 /shi/ and /yon/ : four
五 /go/ : five
六 /ro ku/ : six
七 /shi chi/ and /na na/ : seven
八 /ha chi/ : eight
九 /kyuu/ and /ku/ : nine
十 /juu/ : ten
百 /hya ku/ : hundred
千 /sen/ : thousand
万 /man/ : ten thousand => (value multiplier)
億 /o ku/ : hundred million (ten thousand x ten thousand)
兆 /chou/ : trillion (hundred million x ten thousand)
京 /kyou/ and /kei/ : ten quadrillion (hundred million x ten thousand)
垓 /gai/ : hundred quintillion (ten quadrillion x ten thousand)