81989559 has 12 divisors (see below), whose sum is σ = 119761200. Its totient is φ = 54045024.

The previous prime is 81989539. The next prime is 81989591. The reversal of 81989559 is 95598918.

81989559 is a `hidden beast` number, since 8 + 1 + 9 + 89 + 559 = 666.

It is not a de Polignac number, because 81989559 - 2¹⁹ = 81465271 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81989539) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 50379 + ... + 51980.

It is an arithmetic number, because the mean of its divisors is an integer number (9980100).

Almost surely, 2^81989559 is an apocalyptic number.

81989559 is a gapful number since it is divisible by the number (89) formed by its first and last digit.

81989559 is a deficient number, since it is larger than the sum of its proper divisors (37771641).

81989559 is a wasteful number, since it uses less digits than its factorization.

81989559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102454 (or 102451 counting only the distinct ones).

The product of its digits is 1166400, while the sum is 54.

The square root of 81989559 is about 9054.8086120028. The cubic root of 81989559 is about 434.4297084726.

The spelling of 81989559 in words is "eighty-one million, nine hundred eighty-nine thousand, five hundred fifty-nine".