81007120656 has 360 divisors, whose sum is σ = 297317116320. Its totient is φ = 21040145280.

The previous prime is 81007120651. The next prime is 81007120669. The reversal of 81007120656 is 65602170018.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81007120656.

It is not an unprimeable number, because it can be changed into a prime (81007120651) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 2545515 + ... + 2577141.

Almost surely, 2^81007120656 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 81007120656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (148658558160).

81007120656 is an abundant number, since it is smaller than the sum of its proper divisors (216309995664).

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

81007120656 is a wasteful number, since it uses less digits than its factorization.

81007120656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31680 (or 31650 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The spelling of 81007120656 in words is "eighty-one billion, seven million, one hundred twenty thousand, six hundred fifty-six".