This session will guide you in counting numbers from Zero to trillion in Japanese.
Please download the interactive PDF, have a glance and begin the session below.

Numbers 0~10
Note that Zero in Japanese is often used as ‘ゼロ’ (as it is a borrowed word from a foreign language, it is written in katakana)
And reading ‘れい’ is Japanese reading often used when using decimal numbers.
For example 0.7 = れいてんなな (dot in Japanese is てん) or ゼロてんなな。

Next, observe that Four, Seven and Nine also has two readings.
The readings written in the bracket are used for special purposes, which we will see in our further sessions whenever required.

Numbers 11~100
Counting up to 100 is counting like 1 to 10.
The Hint to remember here is: multiples of 10 + number
For example, 
12 is (10+2)じゅう + に = じゅうに
30 is (30+0)さん + じゅう = さんじゅう
56 is (50+6)さん + じゅう+ろく = さんじゅうろく and so on.

Numbers 101~1000
100 in Japanese is ひゃく.
The Hint to remember here is: multiples of 100 + number
Observe that,
105 is (100+5)ひゃく + ご =ひゃくご
148is (100+40+8)ひゃく+ よんじゅう ＋ はち =ひゃくよんじゅうはち
200 is (2+100)に + ひゃく =にひゃく
But,
300 becomes (3+100)さん + ひゃく = さんびゃく
600 becomes (6+100)ろく + ひゃく = ろっぴゃく
800 becomes (8+100)はち + ひゃく= はっぴゃく

Numbers 1001~10,000
1000 in Japanese is せん.
The Hint to remember here is: multiples of 1000 + number
Observe that,
1009 is (1000+9) which becomes
せん+きゅう =せんきゅう
1996 is (1000+900+90+6) which becomes
せん＋きゅうひゃく+きゅうじゅう＋ろく =せんきゅうひゃくきゅうじゅうろく
2532 is (2000+500+30+2) which becomes
にせん＋ごひゃく+さんじゅう＋ご =にせんごひゃくさんじゅうに
4000 is (4+1000)よん+せん = よんせん
But,
3000 becomes (3+1000)さん+せん=さんぜん and
8000 becomes (8+1000)はち+せん = はっせん

Numbers 10,000~1,000,000,000,000
10,000(ten thousand) in Japanese is いちまん.
1,000,000(million) in Japanese is ひゃくまん.
100,000,000(hundred million) in Japanese is いちおく.
1000,000,000(billion) in Japanese is じゅうおく.
1000,000,000,000(trillion) in Japanese is いっちょう.