81915861 has 4 divisors (see below), whose sum is σ = 109221152. Its totient is φ = 54610572.

The previous prime is 81915833. The next prime is 81915871. The reversal of 81915861 is 16851918.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81915861 - 2¹⁸ = 81653717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81915871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13652641 + ... + 13652646.

It is an arithmetic number, because the mean of its divisors is an integer number (27305288).

Almost surely, 2^81915861 is an apocalyptic number.

It is an amenable number.

81915861 is a deficient number, since it is larger than the sum of its proper divisors (27305291).

81915861 is a wasteful number, since it uses less digits than its factorization.

81915861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27305290.

The product of its digits is 17280, while the sum is 39.

The square root of 81915861 is about 9050.7381466928. The cubic root of 81915861 is about 434.2995040955.

The spelling of 81915861 in words is "eighty-one million, nine hundred fifteen thousand, eight hundred sixty-one".