81636057811968 has 352 divisors, whose sum is σ = 245566155506688. Its totient is φ = 23893858713600.

The previous prime is 81636057811961. The next prime is 81636057811969. The reversal of 81636057811968 is 86911875063618.

It is a tau number, because it is divible by the number of its divisors (352).

It is not an unprimeable number, because it can be changed into a prime (81636057811961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 171053353 + ... + 171529943.

Almost surely, 2^{81636057811968} is an apocalyptic number.

81636057811968 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81636057811968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122783077753344).

81636057811968 is an abundant number, since it is smaller than the sum of its proper divisors (163930097694720).

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

81636057811968 is a wasteful number, since it uses less digits than its factorization.

81636057811968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 476799 (or 476781 counting only the distinct ones).

The product of its (nonzero) digits is 104509440, while the sum is 69.

The spelling of 81636057811968 in words is "eighty-one trillion, six hundred thirty-six billion, fifty-seven million, eight hundred eleven thousand, nine hundred sixty-eight".