81657856 has 72 divisors (see below), whose sum is σ = 188742960. Its totient is φ = 34603008.

The previous prime is 81657841. The next prime is 81657887. The reversal of 81657856 is 65875618.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 917460 + ... + 917548.

It is an arithmetic number, because the mean of its divisors is an integer number (2621430).

Almost surely, 2^81657856 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 81657856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (94371480).

81657856 is an abundant number, since it is smaller than the sum of its proper divisors (107085104).

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

81657856 is an frugal number, since it uses more digits than its factorization.

81657856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130 (or 98 counting only the distinct ones).

The product of its digits is 403200, while the sum is 46.

The square root of 81657856 is about 9036.4736484981. The cubic root of 81657856 is about 433.8430630236.

Subtracting from 81657856 its sum of digits (46), we obtain a triangular number (81657810 = T₁₂₇₇₉).

The spelling of 81657856 in words is "eighty-one million, six hundred fifty-seven thousand, eight hundred fifty-six".