Useful Information

One – 一 (yī)

Two – 二 (èr)

Three – 三 (sān)

Four – 四 (sì)

Five – 五 (wǔ)

Six – 六 (liù)

Seven – 七 (qī)

Eight – 八 (bā)

Nine – 九 (jiǔ)

Ten – 十 (shí)

Two (when used before measure words and before 半，千，万and 亿) – 两 (liǎng)

One (for oral use) – 幺 (yāo)

Hundred – 百 (bǎi)

Thousand – 千 (qiān)

Addition:

个gè – measure word before nouns without special measure words of their own;

for example  “两个苹果(liǎnggèpíngguǒ)” means “two apples”

Twenty, thirty... – 二十、三十...... (èrshí, sānshí...)