Japanese don't have a slang for saying numbers faster, but they have slang for some numbers. For example mahjong hand with the score 500-300 can be called ゴミ(53), which sounds like "trash". Though, it often works the other way around, Japanese people use numbers to either censor NSFW Japanese words, or to shorten common words. オナニ - is written as 072, 殺し - 567, 死 - 4, しこしこ - 4545, マグロ - 096. There are more of them, but these are the ones I remember well. More on reddit.com

Same here. And when I'm reading a text out loud in a foreign language (other than english at least) it's hard and takes a relatively long practice time to not just read it in my native language. More on reddit.com

It's really simple after 20. Every first digit has a prefix: 1 : ek- , 2: ba- , 3: te- , 4: cha- , 5: pa- , 6: ch- , 7: st- , 8: ath- , 9: un- Similarly every tens digit has a corresponding suffix. 20s: -(a)ees , 30s: -atthis, 40s: -nthaalis , 50s: -aawan , 60s: -sut , 70s: -tar , 80s: -aasi , 90s: -aanway So for a number, say 87, you write the unit(7) first and then the tens digit(8) and it becomes sataasi. Or 54 becomes chawan. One thing to remember though is that numbers ending with 9 always have the sound of the next tens digit. For example, 89 is unaanway not unassi ( which is 79) and 69 is unattar not unsut ( which is 59). Of course, this is a heuristic and does not work for every number, eg 53 is trippan not treaawan, but it works for the vast majority of them. If you have any questions, I'd be happy to answer them. Edit: the 30s were wrong. Have fixed them now. More on reddit.com