81866856 has 32 divisors (see below), whose sum is σ = 209024640. Its totient is φ = 26707968.

The previous prime is 81866789. The next prime is 81866857. The reversal of 81866856 is 65866818.

It is a happy number.

It is a super-3 number, since 3×81866856³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (81866857) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35161 + ... + 37416.

It is an arithmetic number, because the mean of its divisors is an integer number (6532020).

Almost surely, 2^81866856 is an apocalyptic number.

It is an amenable number.

81866856 is an abundant number, since it is smaller than the sum of its proper divisors (127157784).

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

81866856 is a wasteful number, since it uses less digits than its factorization.

81866856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72633 (or 72629 counting only the distinct ones).

The product of its digits is 552960, while the sum is 48.

The square root of 81866856 is about 9048.0305039274. The cubic root of 81866856 is about 434.2128823171.

The spelling of 81866856 in words is "eighty-one million, eight hundred sixty-six thousand, eight hundred fifty-six".