Hoffman (1998, p. 90) calls the sum of the exponents in the prime factorization of a number its roundness. The first few values for 
, 2, ... are 0, 1, 1, 2, 1, 2, 1, 3, 2, 2, ... (OEIS A001222).
Roundness
See also
Highly Composite Number, Prime Factorization, Round NumberExplore with Wolfram|Alpha
References
Abramowitz, M. and Stegun, I. A. (Eds.). Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, p. 844, 1972.Hoffman, P. The Man Who Loved Only Numbers: The Story of Paul Erdős and the Search for Mathematical Truth. New York: Hyperion, p. 90, 1998.Kac, M. Statistical Independence in Probability, Analysis, and Number Theory. Buffalo, NY: Math. Assoc. Amer., p. 64, 1959.Sloane, N. J. A. Sequence A001222/M0094 in "The On-Line Encyclopedia of Integer Sequences."Referenced on Wolfram|Alpha
RoundnessCite this as:
Weisstein, Eric W. "Roundness." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Roundness.html