81387811 has 12 divisors (see below), whose sum is σ = 86602824. Its totient is φ = 76471200.

The previous prime is 81387791. The next prime is 81387821. The reversal of 81387811 is 11878318.

It is not a de Polignac number, because 81387811 - 2¹⁷ = 81256739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81387821) 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 11 ways as a sum of consecutive naturals, for example, 46431 + ... + 48151.

It is an arithmetic number, because the mean of its divisors is an integer number (7216902).

Almost surely, 2^81387811 is an apocalyptic number.

81387811 is a deficient number, since it is larger than the sum of its proper divisors (5215013).

81387811 is a wasteful number, since it uses less digits than its factorization.

81387811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1890 (or 1871 counting only the distinct ones).

The product of its digits is 10752, while the sum is 37.

The square root of 81387811 is about 9021.5193288049. The cubic root of 81387811 is about 433.3642908192.

The spelling of 81387811 in words is "eighty-one million, three hundred eighty-seven thousand, eight hundred eleven".