81571817028 has 24 divisors (see below), whose sum is σ = 204975335488. Its totient is φ = 25099020576.

The previous prime is 81571817021. The next prime is 81571817071. The reversal of 81571817028 is 82071817518.

It is a super-2 number, since 2×81571817028² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81571817021) 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, 261447976 + ... + 261448287.

Almost surely, 2^81571817028 is an apocalyptic number.

It is an amenable number.

81571817028 is an abundant number, since it is smaller than the sum of its proper divisors (123403518460).

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

81571817028 is a wasteful number, since it uses less digits than its factorization.

81571817028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522896283 (or 522896281 counting only the distinct ones).

The product of its (nonzero) digits is 250880, while the sum is 48.

The spelling of 81571817028 in words is "eighty-one billion, five hundred seventy-one million, eight hundred seventeen thousand, twenty-eight".