81680 has 20 divisors (see below), whose sum is σ = 190092. Its totient is φ = 32640.

The previous prime is 81677. The next prime is 81689. The reversal of 81680 is 8618.

81680 is nontrivially palindromic in base 7.

It can be written as a sum of positive squares in 2 ways, for example, as 38416 + 43264 = 196^2 + 208^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 431 + ... + 590.

2⁸¹⁶⁸⁰ is an apocalyptic number.

81680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81680 is an abundant number, since it is smaller than the sum of its proper divisors (108412).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95046).

81680 is a wasteful number, since it uses less digits than its factorization.

81680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1034 (or 1028 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 81680 is about 285.7971308463. The cubic root of 81680 is about 43.3882276040.

The spelling of 81680 in words is "eighty-one thousand, six hundred eighty".