81989791 has 16 divisors (see below), whose sum is σ = 91022400. Its totient is φ = 73370880.

The previous prime is 81989771. The next prime is 81989801. The reversal of 81989791 is 19798918.

It is a cyclic number.

It is not a de Polignac number, because 81989791 - 2¹⁷ = 81858719 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81989701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 105681 + ... + 106453.

It is an arithmetic number, because the mean of its divisors is an integer number (5688900).

Almost surely, 2^81989791 is an apocalyptic number.

81989791 is a deficient number, since it is larger than the sum of its proper divisors (9032609).

81989791 is a wasteful number, since it uses less digits than its factorization.

81989791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1026.

The product of its digits is 326592, while the sum is 52.

The square root of 81989791 is about 9054.8214228664. The cubic root of 81989791 is about 434.4301182304.

The spelling of 81989791 in words is "eighty-one million, nine hundred eighty-nine thousand, seven hundred ninety-one".