81211650912 has 576 divisors, whose sum is σ = 293462507520. Its totient is φ = 20756938752.

The previous prime is 81211650911. The next prime is 81211650941. The reversal of 81211650912 is 21905611218.

81211650912 is a `hidden beast` number, since 8 + 121 + 16 + 509 + 12 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81211650911) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 212040673 + ... + 212041055.

It is an arithmetic number, because the mean of its divisors is an integer number (509483520).

Almost surely, 2^81211650912 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 81211650912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146731253760).

81211650912 is an abundant number, since it is smaller than the sum of its proper divisors (212250856608).

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

81211650912 is a wasteful number, since it uses less digits than its factorization.

81211650912 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 715 (or 704 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 36.

The spelling of 81211650912 in words is "eighty-one billion, two hundred eleven million, six hundred fifty thousand, nine hundred twelve".