81931778083584 has 1152 divisors, whose sum is σ = 287040109117440. Its totient is φ = 22726025625600.

The previous prime is 81931778083559. The next prime is 81931778083601. The reversal of 81931778083584 is 48538087713918.

It is a happy number.

81931778083584 is a `hidden beast` number, since 8 + 1 + 9 + 31 + 7 + 7 + 8 + 0 + 8 + 3 + 584 = 666.

It is a tau number, because it is divible by the number of its divisors (1152).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is an unprimeable number.

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 127 ways as a sum of consecutive naturals, for example, 72957949647 + ... + 72957950769.

Almost surely, 2^{81931778083584} 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 81931778083584, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (143520054558720).

81931778083584 is an abundant number, since it is smaller than the sum of its proper divisors (205108331033856).

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

81931778083584 is a wasteful number, since it uses less digits than its factorization.

81931778083584 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1726 (or 1706 counting only the distinct ones).

The product of its (nonzero) digits is 325140480, while the sum is 72.

The spelling of 81931778083584 in words is "eighty-one trillion, nine hundred thirty-one billion, seven hundred seventy-eight million, eighty-three thousand, five hundred eighty-four".