81187865 has 16 divisors (see below), whose sum is σ = 107006400. Its totient is φ = 58643520.

The previous prime is 81187859. The next prime is 81187877. The reversal of 81187865 is 56878118.

It is not a de Polignac number, because 81187865 - 2¹⁰ = 81186841 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 3242 + ... + 13148.

It is an arithmetic number, because the mean of its divisors is an integer number (6687900).

Almost surely, 2^81187865 is an apocalyptic number.

It is an amenable number.

81187865 is a deficient number, since it is larger than the sum of its proper divisors (25818535).

81187865 is a wasteful number, since it uses less digits than its factorization.

81187865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10072.

The product of its digits is 107520, while the sum is 44.

The square root of 81187865 is about 9010.4308997961. The cubic root of 81187865 is about 433.0091167874.

The spelling of 81187865 in words is "eighty-one million, one hundred eighty-seven thousand, eight hundred sixty-five".