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  • AtomQ[ expr ] yields True if expr is an expression which cannot be divided into subexpressions, and yields False otherwise.
  • You can use AtomQ in a recursive procedure to tell when you have reached the bottom of the tree corresponding to an expression.
  • AtomQ gives True for symbols, numbers, strings and other raw objects.
  • AtomQ gives True on any object whose subparts cannot be accessed using functions like Map.
  • See the Mathematica book: Section 2.3.5.
  • See also: NumberQ, Head, LeafCount, Length.

    Further Examples

    Integers, complex numbers, strings, and symbols are all atoms; a list is not an atom.