81865558515 has 32 divisors (see below), whose sum is σ = 141386575680. Its totient is φ = 40209924096.

The previous prime is 81865558451. The next prime is 81865558517. The reversal of 81865558515 is 51585556818.

It is not a de Polignac number, because 81865558515 - 2⁶ = 81865558451 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81865558517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 400350 + ... + 569219.

It is an arithmetic number, because the mean of its divisors is an integer number (4418330490).

Almost surely, 2^81865558515 is an apocalyptic number.

81865558515 is a deficient number, since it is larger than the sum of its proper divisors (59521017165).

81865558515 is a wasteful number, since it uses less digits than its factorization.

81865558515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 970023.

The product of its digits is 9600000, while the sum is 57.

The spelling of 81865558515 in words is "eighty-one billion, eight hundred sixty-five million, five hundred fifty-eight thousand, five hundred fifteen".