It could be a lot of things. It could be a mammillaria, or not. Too bad the focus is crisp on the wall paper and not the cactus.
I strongly suggest you submit another image in better focus.

Thank you for answering. Sorry the focus is bad. I took the picture with my webcam and then edited it in Photobucket where I altered the focus because I thought it would give a better colour. However I know nothing at all about photography. This picture now are taken without altering the focus.Since I could not send the other one I have just taken I shall send it after this one. It is the best I can do. Please let me know if it is better. If it is I shall not alter any focus again.

Here is the second picture.

Although I have not seen one so tall, perhaps it is Mammillaria longimamma (Syn: Dolichothele longimamma).

To get the plant in better focus, perhaps you could try moving it further away from your webcam (making sure you had good lighting).

Hello,

It is indeed a Mammillaria Longimamma as you said. After my looking after it properly a few months it is now robust and has sharp thorns as it said in the description I found on the web. I shall now move it from the window facing north to one facing south where it wil get all the light and bright sunshine when it is that sunny. Thank you all for your kind help.

I tried many times to enter a URL to the image on Photobucket by copying and pasting the html link for it on Photobucket but every time the message was rejected. It was very frustrating. Finally I found the option to upload an image file.

Kind regards,
Edwin

It looks great, Edwin!

When using Photobucket (I know it can be frustrating), you have to get the HTML code link for your pic. The url will not work. Glad you figured an alternate solution. =)

Thank you, Rosemariero.I think it looks good too and look forward to seeing it bloom some time. It was the HTML link I copied. Since it was a long time since I posted to this forum I had forgotten where the Browse was for adding images to a message. I only have 3 types of cacti: Nopalxochia, Holiday Cactus (blooms in November so it is called November Cactus here) and the Mammillaria Longimamma. The first 2 thrive on coffee grounds, the Mammillaria on my urine diluted with 30 parts water as it likes slightly alkaline soil and I use no commercial fertilizer for any of my propagation. Otherwise I would have uploaded directly from My images (or perhaps it is My pictures in English?) as I usually do. I much prefer that alternative. Before I found Browse I tried copying and pasting the Direct link on Photobucket. It works but the picture is not shown in the message but a link to it. Browsing gets the picture shown in the message which is what I want done.