Did he also memorize Xue Tian's number?
The answer is... no.
There was a reason why he remembered Chang Jianyu's number, and it was because he had often been in dangerous situations in the past, and he would need someone to help him if danger lurked him.
That was why Wen Xiang deliberately remembered Chang Jianyu's number, thinking that if he was really close to the door of death, he could contact the man and ask the man to save him as soon as possible even if they were away from each other.
That was also what happened when he tried to escape from the Black Lotus. At that time, he had Chang Jianyu on his speed dial, but he knew that he couldn't always rely on his own phone if the situation was more dangerous than that.
That was the reason why he ended up memorizing Chang Jianyu's number, thinking that it would be useful if he didn't hold onto his phone, like the current situation.
