81491535 has 16 divisors (see below), whose sum is σ = 144874080. Its totient is φ = 43462080.

The previous prime is 81491519. The next prime is 81491569. The reversal of 81491535 is 53519418.

81491535 is a `hidden beast` number, since 81 + 49 + 1 + 535 = 666.

It is not a de Polignac number, because 81491535 - 2⁴ = 81491519 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81491535.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 301686 + ... + 301955.

It is an arithmetic number, because the mean of its divisors is an integer number (9054630).

Almost surely, 2^81491535 is an apocalyptic number.

81491535 is a deficient number, since it is larger than the sum of its proper divisors (63382545).

81491535 is a wasteful number, since it uses less digits than its factorization.

81491535 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 603655 (or 603649 counting only the distinct ones).

The product of its digits is 21600, while the sum is 36.

The square root of 81491535 is about 9027.2661974709. The cubic root of 81491535 is about 433.5483118053.

The spelling of 81491535 in words is "eighty-one million, four hundred ninety-one thousand, five hundred thirty-five".