>>1The plane of Numbers is one of higher mental planes.
(There are planes of Concepts, Words, Ideas and similar mental categories, some of which overlap or are embedded inside one another). To enter this plane you need to align your chakras with Higher Mental planes(Use mudras which boost Akasha/ether element which align to Higher Mental( and Etheric)) and meditate on a specific number which would be your vehicle to enter the plane(e.g. 22 visualize it on area around the third eye).
Binaural beats may help you to maintain focus(Lambda range corresponds to higher mental) and strict diet for stable projection. Also, numbers are beings(who have own consciousness) and by giving them focused energy you give them power in their plane(plane of Numbers) and since numbers plane influences all below it will cause changes in the worlds.
By giving all your energy to one number(e.g. 22) it could amass enough power to forge its own plane/subplane which would be a "dubs plane", a distinct area in mental planes(similar to enpowered numbers such as 666,420, pi and golden ratio,etc). However i don't recommend it unless you really know what you're doing.