81988433856 has 504 divisors, whose sum is σ = 280134706176. Its totient is φ = 22853698560.

The previous prime is 81988433837. The next prime is 81988433869. The reversal of 81988433856 is 65833488918.

81988433856 is a `hidden beast` number, since 8 + 198 + 8 + 433 + 8 + 5 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (504).

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

It is a junction number, because it is equal to n+sod(n) for n = 81988433793 and 81988433802.

It is a congruent number.

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 71 ways as a sum of consecutive naturals, for example, 361182415 + ... + 361182641.

Almost surely, 2^81988433856 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 81988433856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (140067353088).

81988433856 is an abundant number, since it is smaller than the sum of its proper divisors (198146272320).

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

81988433856 is a wasteful number, since it uses less digits than its factorization.

81988433856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 517 (or 497 counting only the distinct ones).

The product of its digits is 39813120, while the sum is 63.

The spelling of 81988433856 in words is "eighty-one billion, nine hundred eighty-eight million, four hundred thirty-three thousand, eight hundred fifty-six".