81691078 has 32 divisors (see below), whose sum is σ = 148561920. Its totient is φ = 32931360.

The previous prime is 81691039. The next prime is 81691081. The reversal of 81691078 is 87019618.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 81691078.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17563 + ... + 21721.

It is an arithmetic number, because the mean of its divisors is an integer number (4642560).

Almost surely, 2^81691078 is an apocalyptic number.

81691078 is a deficient number, since it is larger than the sum of its proper divisors (66870842).

81691078 is a wasteful number, since it uses less digits than its factorization.

81691078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4252.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 81691078 is about 9038.3116786267. The cubic root of 81691078 is about 433.9018905133.

The spelling of 81691078 in words is "eighty-one million, six hundred ninety-one thousand, seventy-eight".