81223855872 has 72 divisors (see below), whose sum is σ = 216289694544. Its totient is φ = 27060117504.

The previous prime is 81223855871. The next prime is 81223855891. The reversal of 81223855872 is 27855832218.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81223855871) 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, 1457188 + ... + 1511900.

Almost surely, 2^81223855872 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81223855872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (108144847272).

81223855872 is an abundant number, since it is smaller than the sum of its proper divisors (135065838672).

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

81223855872 is a wasteful number, since it uses less digits than its factorization.

81223855872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56665 (or 56651 counting only the distinct ones).

The product of its digits is 2150400, while the sum is 51.

The spelling of 81223855872 in words is "eighty-one billion, two hundred twenty-three million, eight hundred fifty-five thousand, eight hundred seventy-two".