In Mandarin Chinese, 十 (Pinyin: shí 🔊) is a word for number “ten”. It also means “complete” or “topmost”, as in 十全十美 (shí quán shí měi), an idiom for “perfect in every way”. So shí is perfect, and if you happen to know a lady who is perfect in every way, that could help you to remember the pronunciation: “She is perfect”.
In contrast to 一 “one”, the symbol for ten was historically represented by a single vertical stroke 丨, which sometimes had a dot or a “swelling” in the middle. According to Ponte Ryūrui, the second stroke in the modern character 十 is just “an aesthetically altered fat dot”. The similarity between the Roman numeral Ⅹ and 十 makes this latter an easy character to remember.
There are several Chinese hand signs for “ten”. For example, the crossed index and middle fingers on one hand, or the index fingers of both hands crossed making the 十.
There is another hanzi with the same meaning, 拾, which is mainly used for accounting purposes.