81686751 has 16 divisors (see below), whose sum is σ = 115884288. Its totient is φ = 51004800.

The previous prime is 81686743. The next prime is 81686791. The reversal of 81686751 is 15768618.

It is not a de Polignac number, because 81686751 - 2³ = 81686743 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81686701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6966 + ... + 14556.

It is an arithmetic number, because the mean of its divisors is an integer number (7242768).

Almost surely, 2^81686751 is an apocalyptic number.

81686751 is a deficient number, since it is larger than the sum of its proper divisors (34197537).

81686751 is a wasteful number, since it uses less digits than its factorization.

With its successor (81686752) it forms an eRAP, since the sums of their prime factors are consecutive (7822 and 7823).

81686751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7822.

The product of its digits is 80640, while the sum is 42.

The square root of 81686751 is about 9038.0723055306. The cubic root of 81686751 is about 433.8942294293.

The spelling of 81686751 in words is "eighty-one million, six hundred eighty-six thousand, seven hundred fifty-one".