How do I know when my son is ready to potty train?

For the last few days my son has come to me a ton of times pulling at his diapers and squealing at me. Also when he’s dirty he comes and motions to be picked up and when we hold him he puts his knees together. Like he won’t spread his legs to make it easier to be held and if he’s sat down on his butt he screams and rolls over. It’s like he doesn’t want to diaper touching him. But he’s fine if it’s dry. But when he knows I’m about to change him he lays down and is ready but when I pull out the diaper he takes it and throws it. Is he ready to be potty trained???? He’s old 13.5 months old. I mean he’s still a baby he’s barely over a year old. And he walks like 75% of the time but he still does a lot of crawling. Would that matter? He’s my first and I’m pregnant with my second but I already know potty training her will be different because she’s a girl. And I wasn’t in the picture when my 6 year old bonus baby was potty training.