In number theory, a semiperfect number or pseudoperfect number is a natural number n that is equal to the sum of all or some of its proper divisors. A...

natural number following 79 and preceding 81. 80 is: the sum of Euler's totient function φ(x) over the first sixteen integers. a semiperfect number, since...

abundant number; smallest odd primitive semiperfect number; Leyland number 946 = 2 × 11 × 43, sphenic number, 43rd triangular number, hexagonal number, happy...

is the natural number following 17 and preceding 19. It is an even composite number. 18 is a semiperfect number and an abundant number. It is a largely...

the 3-aliquot tree. From 1 to the number 30, this is the longest Aliquot Sequence. It is also: A semiperfect number, since adding some subsets of its...

refactorable number, since 8 is one of its 8 divisors. The sum of the sums of the divisors of the first 8 positive integers. A semiperfect number, since 56...

g., 6, 12, and 18) gives 36; hence, it is also the eighth semiperfect number. This number is the sum of the cubes of the first three positive integers...

the sum of a subset of its divisors, it is also the twenty-first semiperfect number. An angle measuring 90 degrees is called a right angle. In normal...

natural number following 87 and preceding 89. 88 is: a refactorable number. a primitive semiperfect number. an untouchable number. a hexadecagonal number. an...

composite number, the smallest abundant number, a semiperfect number, a highly composite number, a refactorable number, and a Pell number. It is the...

number following 65 and preceding 67. 66 is a sphenic number, a semiperfect number, and a Erdős–Woods number. It is also the 11th triangular number and...

(eighty-four) is the natural number following 83 and preceding 85. It is seven dozens. 84 is a semiperfect number, being thrice a perfect number, and the sum of the...

perfect number. Most abundant numbers are also semiperfect; abundant numbers which are not semiperfect are called weird numbers. Hyperperfect number Multiply...

semiperfect number. These proper divisors can be summed in various ways to express all positive integers smaller than 54, so 54 is a practical number...

the 3-aliquot tree. a semiperfect number, as a multiple of a perfect number. the 12th triangular number. a palindromic number in bases 5 (3035), 7 (1417)...

octagonal number. a refactorable number. an untouchable number. a semiperfect number since it is a multiple of 6. an abundant number since the sum of its proper...

a prime number. 350 = 2 × 52 × 7 = { 7 4 } {\displaystyle \left\{{7 \atop 4}\right\}} , primitive semiperfect number, divisible by the number of primes...

two) is the natural number following 101 and preceding 103. 102 is an abundant number and a semiperfect number. It is a sphenic number. The sum of Euler's...

eight) is the natural number following 107 and preceding 109. 108 is: an abundant number. a semiperfect number. a tetranacci number. the hyperfactorial...

In number theory, a weird number is a natural number that is abundant but not semiperfect. In other words, the sum of the proper divisors (divisors including...

100 can be expressed as a sum of some of its divisors, making it a semiperfect number. The geometric mean of its nine divisors is 10. 100 is the sum of...

primitive semiperfect number meaning that it is a semiperfect number that is not divisible by any other semiperfect number. 304 is an untouchable number meaning...

[and] four) is the natural number following 103 and preceding 105. 104 is a refactorable number and a primitive semiperfect number. The smallest known 4-regular...

abundant number which is not a semiperfect number is called a weird number. An abundant number with abundance 1 is called a quasiperfect number, although...

It is a semiperfect number, equal to the concatenation of two of its proper divisors (24 and 40). It is also the 12th highly composite number, with 20...

576 or 242, which divides 1728 thrice over. 1728 is an abundant and semiperfect number, as it is smaller than the sum of its proper divisors yet equal to...

Quasiperfect number Almost perfect number Multiply perfect number Hyperperfect number Semiperfect number Primitive semiperfect number Unitary perfect number Weird...

forty four) is the natural number following 743 and preceding 745. 744 is a semiperfect number. It is also an abundant number. The j-invariant, an important...

natural number following 175 and preceding 177. 176 is an even number and an abundant number. It is an odious number, a self number, a semiperfect number, and...

abundant number, but no subset sums to 836, so it is not a semiperfect number; therefore it is a weird number. Besides, 836 is the smallest weird number that...