81685767 has 16 divisors (see below), whose sum is σ = 111837440. Its totient is φ = 53004672.

The previous prime is 81685757. The next prime is 81685777. The reversal of 81685767 is 76758618.

It is an interprime number because it is at equal distance from previous prime (81685757) and next prime (81685777).

It is not a de Polignac number, because 81685767 - 2¹⁸ = 81423623 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81685727) 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, 42534 + ... + 44412.

It is an arithmetic number, because the mean of its divisors is an integer number (6989840).

Almost surely, 2^81685767 is an apocalyptic number.

81685767 is a deficient number, since it is larger than the sum of its proper divisors (30151673).

81685767 is a wasteful number, since it uses less digits than its factorization.

81685767 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2262.

The product of its digits is 564480, while the sum is 48.

The square root of 81685767 is about 9038.0178689799. The cubic root of 81685767 is about 433.8924871899.

The spelling of 81685767 in words is "eighty-one million, six hundred eighty-five thousand, seven hundred sixty-seven".