is a slang term used in Computer engineering
to refer to any computing operation that requires a large number of arithmetic operations (adding, subtracting, multiplying and dividing) - as opposed to (for example) memory reads and writes, accesses to disk drives or networking operations. By extension, a Number cruncher
is either a computer that is dedicated to that kind of processing because of its role in some organisation - or a computer CPU
that is especially designed to be good at arithmetic operations (typically at the cost of being worse at other things).
The term Number cruncher is occasionally used to refer to a piece of software that requires the computer to perform unusually large amounts of number crunching - although that usage of the term is rare.
Most Supercomputers are designed to be efficient number crunchers before all else, small embedded computers are often very poor number crunchers with desktop PCs falling somewhere in between.