80991 has 6 divisors (see below), whose sum is σ = 117000. Its totient is φ = 53988.

The previous prime is 80989. The next prime is 81001. The reversal of 80991 is 19908.

It is not a de Polignac number, because 80991 - 2¹ = 80989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (80911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4491 + ... + 4508.

It is an arithmetic number, because the mean of its divisors is an integer number (19500).

2⁸⁰⁹⁹¹ is an apocalyptic number.

80991 is a deficient number, since it is larger than the sum of its proper divisors (36009).

80991 is a wasteful number, since it uses less digits than its factorization.

80991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9005 (or 9002 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 80991 is about 284.5891775876. The cubic root of 80991 is about 43.2658845503.

Adding to 80991 its sum of digits (27), we get a palindrome (81018).

It can be divided in two parts, 8099 and 1, that added together give a square (8100 = 90²).

The spelling of 80991 in words is "eighty thousand, nine hundred ninety-one".