81947693520 has 800 divisors, whose sum is σ = 375758735616. Its totient is φ = 16024780800.

The previous prime is 81947693497. The next prime is 81947693533. The reversal of 81947693520 is 2539674918.

81947693520 is a `hidden beast` number, since 8 + 19 + 47 + 69 + 3 + 520 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 8477490 + ... + 8487150.

It is a 1-persistent number, because it is pandigital, but 2⋅81947693520 = 163895387040 is not.

Almost surely, 2^81947693520 is an apocalyptic number.

81947693520 is a gapful number since it is divisible by the number (80) 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 81947693520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (187879367808).

81947693520 is an abundant number, since it is smaller than the sum of its proper divisors (293811042096).

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

81947693520 is a wasteful number, since it uses less digits than its factorization.

81947693520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9721 (or 9706 counting only the distinct ones).

The product of its (nonzero) digits is 3265920, while the sum is 54.

The spelling of 81947693520 in words is "eighty-one billion, nine hundred forty-seven million, six hundred ninety-three thousand, five hundred twenty".