81866051568 has 160 divisors (see below), whose sum is σ = 269627742720. Its totient is φ = 23296896000.

The previous prime is 81866051557. The next prime is 81866051587. The reversal of 81866051568 is 86515066818.

81866051568 is a `hidden beast` number, since 8 + 1 + 8 + 6 + 60 + 515 + 68 = 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 31 ways as a sum of consecutive naturals, for example, 705096 + ... + 812952.

It is an arithmetic number, because the mean of its divisors is an integer number (1685173392).

Almost surely, 2^81866051568 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 81866051568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134813871360).

81866051568 is an abundant number, since it is smaller than the sum of its proper divisors (187761691152).

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

81866051568 is a wasteful number, since it uses less digits than its factorization.

81866051568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108132 (or 108120 counting only the distinct ones).

The product of its (nonzero) digits is 2764800, while the sum is 54.

The spelling of 81866051568 in words is "eighty-one billion, eight hundred sixty-six million, fifty-one thousand, five hundred sixty-eight".