81906811 has 4 divisors (see below), whose sum is σ = 93607792. Its totient is φ = 70205832.

The previous prime is 81906719. The next prime is 81906823. The reversal of 81906811 is 11860918.

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

It is a cyclic number.

It is not a de Polignac number, because 81906811 - 2⁹ = 81906299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81906911) 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, 5850480 + ... + 5850493.

It is an arithmetic number, because the mean of its divisors is an integer number (23401948).

Almost surely, 2^81906811 is an apocalyptic number.

81906811 is a deficient number, since it is larger than the sum of its proper divisors (11700981).

81906811 is a wasteful number, since it uses less digits than its factorization.

81906811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11700980.

The product of its (nonzero) digits is 3456, while the sum is 34.

The square root of 81906811 is about 9050.2381736615. The cubic root of 81906811 is about 434.2835098170.

The spelling of 81906811 in words is "eighty-one million, nine hundred six thousand, eight hundred eleven".