81591029472 has 48 divisors (see below), whose sum is σ = 223488478080. Its totient is φ = 26014530432.

The previous prime is 81591029461. The next prime is 81591029473. The reversal of 81591029472 is 27492019518.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591029473) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18474022 + ... + 18478437.

It is an arithmetic number, because the mean of its divisors is an integer number (4656009960).

Almost surely, 2^81591029472 is an apocalyptic number.

It is an amenable number.

81591029472 is an abundant number, since it is smaller than the sum of its proper divisors (141897448608).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81591029472 is a wasteful number, since it uses less digits than its factorization.

81591029472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36952495 (or 36952487 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 48.

The spelling of 81591029472 in words is "eighty-one billion, five hundred ninety-one million, twenty-nine thousand, four hundred seventy-two".