Basically, 46 Hiraganas + 46 Katakanas. 92 characters in total of them. Plus couple of thousands Kanjis.. But it doesn't mean you have to learn all of them. I suppose that even native Japanese people don't know all kanjis. Maybe for a foreigner, memorizing approx 800 kanjis will be the good first step to understand ordinary Japanese sentences. Once again, you don't have to memorize all!! http://blog-imgs-34.fc2.com/m/a/m/mamanoyumekoubou/20100128134206cd0.jpg ----- 基本的には、 ひらがな　ｘ　４６文字 カタカナ　ｘ　４６文字 の合計　92　文字になります。 に数千文字の漢字が足された形になります。 しかし、ひらがなとカタカナに関しては、昔はもっとあったようです。

Hiragana: 104, with all the additional sounds. Katakana: 104, all additional sounds. Kanji: Total of 50 000.

For the first stage you may learn by heart the first kanji-words. Of those here is equal to 214 traditional radicals. So it would not much for starting. You may find additional information here, if it will be interested for you. http://kanjialive.uchicago.edu/

I used to be good at mathematic though?

Actually 46 and 46 makes 92.