400 million people are using ChatGPT every single week

I made a note of this story when I saw it the other week, because it's just astonishing.
It's an article by Kate Rooney over at CNBC. She details that OpenAI is getting around 400 million weekly active users and that this is up 33% in the last three months.
While Kate's angle is very much focused on DeepSeek and OpenAI, but I thought it was worthwhile documenting this fact for posterity and just as a base reminder to everyone.
400 million users is a lot of people.
A lot.
And just in case you're wondering about growth: This figure was 300 million in December.
Where is it gonna be in six months? 600 million?
What's the upper limit with this?
Fascinating!