Kissing number for $\mathbb{R}^{3}$

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The maximum number of non-overlapping unit spheres that can touch a central unit sphere in $\mathbb{R}^{3}$.
Value: $12$
Updates
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Lower bound: $12$
Reference unknown
[via Kissing number - Wikipedia] -
Upper bound: $12$
Reference unknown
[via Kissing number - Wikipedia]