Prominent Protestant Church historian Mark Noll has written a helpful introduction to Protestantism entitled Protestantism, A Very Short Introduction in a series of books published by Oxford University Press in London England.
I have posted similar facts in the past, based on the two-volume World Christian Encyclopedia. The same facts are available from other resources as well, but this one is succinct and to the point and from a respected and prominent church historian.
“It is challenging to write a coherent history [of Protestantism] because of the sheer multiplicity of Protestant and Protestant-like churches in the world today. The Atlas of World Christianity, published in 2010, counts more than 4,000,000 individual congregations worldwide, with most of them gathered into more than 38,000 Protestant denominations.” (pg. 9)