81195617664 has 192 divisors, whose sum is σ = 268199412000. Its totient is φ = 23096918016.

The previous prime is 81195617653. The next prime is 81195617669. The reversal of 81195617664 is 46671659118.

81195617664 is a `hidden beast` number, since 8 + 1 + 1 + 9 + 561 + 76 + 6 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

It is a self number, because there is not a number n which added to its sum of digits gives 81195617664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81195617669) 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 23 ways as a sum of consecutive naturals, for example, 1824672 + ... + 1868640.

Almost surely, 2^81195617664 is an apocalyptic number.

81195617664 is a gapful number since it is divisible by the number (84) 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 81195617664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134099706000).

81195617664 is an abundant number, since it is smaller than the sum of its proper divisors (187003794336).

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

81195617664 is a wasteful number, since it uses less digits than its factorization.

81195617664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44225 (or 44210 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 54.

The spelling of 81195617664 in words is "eighty-one billion, one hundred ninety-five million, six hundred seventeen thousand, six hundred sixty-four".