81947593728 has 1584 divisors, whose sum is σ = 342487401984. Its totient is φ = 19229736960.

The previous prime is 81947593691. The next prime is 81947593771. The reversal of 81947593728 is 82739574918.

81947593728 is a `hidden beast` number, since 8 + 1 + 9 + 475 + 93 + 72 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (1584).

It is a Harshad number since it is a multiple of its sum of digits (63).

Its product of digits (30481920) is a multiple of the sum of its prime factors (120).

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 1743565801 + ... + 1743565847.

Almost surely, 2^81947593728 is an apocalyptic number.

81947593728 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 81947593728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (171243700992).

81947593728 is an abundant number, since it is smaller than the sum of its proper divisors (260539808256).

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

81947593728 is a wasteful number, since it uses less digits than its factorization.

81947593728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120 (or 83 counting only the distinct ones).

The product of its digits is 30481920, while the sum is 63.

The spelling of 81947593728 in words is "eighty-one billion, nine hundred forty-seven million, five hundred ninety-three thousand, seven hundred twenty-eight".