81685887 has 8 divisors (see below), whose sum is σ = 109003440. Its totient is φ = 54412800.

The previous prime is 81685841. The next prime is 81685937. The reversal of 81685887 is 78858618.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81685887 - 2¹⁵ = 81653119 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81685787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6562 + ... + 14367.

It is an arithmetic number, because the mean of its divisors is an integer number (13625430).

Almost surely, 2^81685887 is an apocalyptic number.

81685887 is a deficient number, since it is larger than the sum of its proper divisors (27317553).

81685887 is a wasteful number, since it uses less digits than its factorization.

81685887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22233.

The product of its digits is 860160, while the sum is 51.

The square root of 81685887 is about 9038.0245076012. The cubic root of 81685887 is about 433.8926996589.

The spelling of 81685887 in words is "eighty-one million, six hundred eighty-five thousand, eight hundred eighty-seven".