81389881 has 4 divisors (see below), whose sum is σ = 81631732. Its totient is φ = 81148032.

The previous prime is 81389873. The next prime is 81389953. The reversal of 81389881 is 18898318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5978025 + 75411856 = 2445^2 + 8684^2 .

It is a cyclic number.

It is not a de Polignac number, because 81389881 - 2³ = 81389873 is a prime.

It is a super-2 number, since 2×81389881² = 13248625458388322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81389281) 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, 120420 + ... + 121093.

It is an arithmetic number, because the mean of its divisors is an integer number (20407933).

Almost surely, 2^81389881 is an apocalyptic number.

It is an amenable number.

81389881 is a deficient number, since it is larger than the sum of its proper divisors (241851).

81389881 is a wasteful number, since it uses less digits than its factorization.

81389881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241850.

The product of its digits is 110592, while the sum is 46.

The square root of 81389881 is about 9021.6340537621. The cubic root of 81389881 is about 433.3679648193.

The spelling of 81389881 in words is "eighty-one million, three hundred eighty-nine thousand, eight hundred eighty-one".