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80 = 245
BaseRepresentation
bin1010000
32222
41100
5310
6212
7143
oct120
988
1080
1173
1268
1362
145a
1555
hex50

80 has 10 divisors (see below), whose sum is σ = 186. Its totient is φ = 32.

The previous prime is 79. The next prime is 83. The reversal of 80 is 8.

80 is nontrivially palindromic in base 3, base 6, base 9 and base 15.

It is a Cunningham number, because it is equal to 34-1.

80 is an esthetic number in base 6, because in such base it adjacent digits differ by 1.

It can be written as a sum of positive squares in only one way, i.e., 64 + 16 = 8^2 + 4^2 .

It is a tau number, because it is divible by the number of its divisors (10).

It is a Harshad number since it is a multiple of its sum of digits (8).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

80 is an undulating number in base 6.

80 is a nontrivial repdigit in base 3, base 9 and base 15.

It is a plaindrome in base 3, base 9, base 12, base 14 and base 15.

It is a nialpdrome in base 3, base 4, base 5, base 9, base 10, base 11, base 13, base 15 and base 16.

It is a zygodrome in base 3, base 4, base 9 and base 15.

It is a congruent number.

Being equal to 3×33-1, it is a generalized Woodall number.

It is a pernicious number, because its binary representation contains a prime number (2) of ones.

In principle, a polygon with 80 sides can be constructed with ruler and compass.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14 + ... + 18.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 80, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93).

80 is an abundant number, since it is smaller than the sum of its proper divisors (106).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

80 is a wasteful number, since it uses less digits than its factorization.

80 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13 (or 7 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 80 is about 8.9442719100. The cubic root of 80 is about 4.3088693801.

The spelling of 80 in words is "eighty", and is thus an aban number, an oban number, and an uban number.

Divisors: 1 2 4 5 8 10 16 20 40 80