Cacti-expert? Help...

[cactwhy]

I know nothing about plants. I'm surprised it's still alive.

Had this cactus over a decade (no idea what type) flowers multiple times a year, and it's always had this white stuff at the bottom, which is now quite high, what is it? Can I get rid of it? (Photo should be attached, but I'm on the app - didn't work for me last time.)

It's half falling over because I didn't know you were supposed to take the babies off, and they had got quite large and were supporting it until I recently removed and repotted them. (Hence the milk carton...😬)

I don't really want it to die, can anyone help?

It's a very old cactus - a Rebutia by the looks of it. The lower part seems to be corking, which is natural and just old age, so you can't get rid of it.
The pups it has produced are also a natural development in this species, so not necessary to remove them normally. However, if you want to rejuvenate it, you could remove some lower ones and root them up for new plants, easy to do at this time of year. Gently take them off, maybe with a sharp knife inserted between the bodies, leave them to dry (callus) in a shady place for a week or so, then sit them on top of some very gritty dry compost and they should start to produce roots in a few weeks, when you can start to gradually water them lightly. They can then be potted up in smallish pots in the same gritty compost.
Hopefully they will flower for you next spring!

Thank you. Going to stake the 'mother' cactus in an attempt to straighten her up! Glad it's not rotting, hopefully the babies will survive!

NanTheWiser in right in everything. Suggest you don't take all the pups off at once. Try one or two - if it works, you can deal with the rest next year.

The plant's actually looking pretty healthy - well done!

If any of the flowers produce a fruit, you can let those ripen - Rebutias are one of the easier cacti to grow from seed.

A lot of cacti use falling over as a way of getting their pups into fresh soil - left to its own devices, the plant will topple, and some of the offsets will start putting roots down. Other types of cacti may simply fall over and throw up a new bunch of offsets from the base.

How sensible / clever of a cactus to fall over to give its pups a flying start!