Weird number

The term "weird number" also refers to a phenomenon in two's complement arithmetic.
Euler diagram of numbers under 100:
   Abundant
   Primitive abundant
   Highly abundant
   Superabundant and highly composite
   Colossally abundant and superior highly composite
   Weird
   Perfect
   Composite
   Deficient

In number theory, a weird number is a natural number that is abundant but not semiperfect.[1][2] In other words, the sum of the proper divisors (divisors including 1 but not itself) of the number is greater than the number, but no subset of those divisors sums to the number itself.

  1. ^ Benkoski, Stan (August–September 1972). "E2308 (in Problems and Solutions)". The American Mathematical Monthly. 79 (7): 774. doi:10.2307/2316276. JSTOR 2316276.
  2. ^ Richard K. Guy (2004). Unsolved Problems in Number Theory. Springer-Verlag. ISBN 0-387-20860-7. OCLC 54611248. Section B2.