81939811 has 4 divisors (see below), whose sum is σ = 83845432. Its totient is φ = 80034192.

The previous prime is 81939787. The next prime is 81939829. The reversal of 81939811 is 11893918.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81939811 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81937811) 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 3 ways as a sum of consecutive naturals, for example, 952746 + ... + 952831.

It is an arithmetic number, because the mean of its divisors is an integer number (20961358).

Almost surely, 2^81939811 is an apocalyptic number.

81939811 is a deficient number, since it is larger than the sum of its proper divisors (1905621).

81939811 is a wasteful number, since it uses less digits than its factorization.

81939811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1905620.

The product of its digits is 15552, while the sum is 40.

The square root of 81939811 is about 9052.0611465014. The cubic root of 81939811 is about 434.3418258121.

The spelling of 81939811 in words is "eighty-one million, nine hundred thirty-nine thousand, eight hundred eleven".