What is the style of art in which small numbers are used to paint pictures called?

We know that, for example,

impressionist painting is a style of art which uses small, thin, yet visible brush strokes,
cubist painting is a style of art that stresses abstract structure,
and so on.

So, my question is, what is the style of art in which small numbers are used to paint pictures (as in the picture below) called?

Numberism - Here is an Einstein.

From the comments - read about the origins.

Besides numberism, the term “coarse-grained pointillism” has been used. Beginning in the late 1960's Ken Knowlton at Bell Labs experimented with “photomosaic, creating large prints from collections of small symbols or images.” A variety of forms appear at knowltonmosaics.com.