81535909 has 24 divisors (see below), whose sum is σ = 101777280. Its totient is φ = 63955008.

The previous prime is 81535879. The next prime is 81535931. The reversal of 81535909 is 90953518.

It is not a de Polignac number, because 81535909 - 2⁵ = 81535877 is a prime.

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81535939) 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 23 ways as a sum of consecutive naturals, for example, 185512 + ... + 185950.

It is an arithmetic number, because the mean of its divisors is an integer number (4240720).

Almost surely, 2^81535909 is an apocalyptic number.

It is an amenable number.

81535909 is a deficient number, since it is larger than the sum of its proper divisors (20241371).

81535909 is a wasteful number, since it uses less digits than its factorization.

81535909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 629 (or 616 counting only the distinct ones).

The product of its (nonzero) digits is 48600, while the sum is 40.

The square root of 81535909 is about 9029.7236391819. The cubic root of 81535909 is about 433.6269898421.

The spelling of 81535909 in words is "eighty-one million, five hundred thirty-five thousand, nine hundred nine".