81686643 has 16 divisors (see below), whose sum is σ = 118348800. Its totient is φ = 49926240.

The previous prime is 81686617. The next prime is 81686651. The reversal of 81686643 is 34668618.

It is a happy number.

It is not a de Polignac number, because 81686643 - 2¹⁶ = 81621107 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81686595 and 81686604.

It is not an unprimeable number, because it can be changed into a prime (81686653) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21348 + ... + 24881.

It is an arithmetic number, because the mean of its divisors is an integer number (7396800).

Almost surely, 2^81686643 is an apocalyptic number.

81686643 is a deficient number, since it is larger than the sum of its proper divisors (36662157).

81686643 is a wasteful number, since it uses less digits than its factorization.

81686643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46282.

The product of its digits is 165888, while the sum is 42.

The square root of 81686643 is about 9038.0663308033. The cubic root of 81686643 is about 433.8940382086.

The spelling of 81686643 in words is "eighty-one million, six hundred eighty-six thousand, six hundred forty-three".