81681860 has 24 divisors (see below), whose sum is σ = 184727256. Its totient is φ = 30159360.

The previous prime is 81681841. The next prime is 81681883. The reversal of 81681860 is 6818618.

It can be written as a sum of positive squares in 4 ways, for example, as 6061444 + 75620416 = 2462^2 + 8696^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156821 + ... + 157340.

It is an arithmetic number, because the mean of its divisors is an integer number (7696969).

Almost surely, 2^81681860 is an apocalyptic number.

It is an amenable number.

81681860 is an abundant number, since it is smaller than the sum of its proper divisors (103045396).

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

81681860 is a wasteful number, since it uses less digits than its factorization.

81681860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 314183 (or 314181 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 38.

The square root of 81681860 is about 9037.8017238707. The cubic root of 81681860 is about 433.8855694406.

The spelling of 81681860 in words is "eighty-one million, six hundred eighty-one thousand, eight hundred sixty".