81691366118 has 4 divisors (see below), whose sum is σ = 122537049180. Its totient is φ = 40845683058.

The previous prime is 81691366069. The next prime is 81691366123. The reversal of 81691366118 is 81166319618.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20422841528 + ... + 20422841531.

It is an arithmetic number, because the mean of its divisors is an integer number (30634262295).

Almost surely, 2^81691366118 is an apocalyptic number.

81691366118 is a deficient number, since it is larger than the sum of its proper divisors (40845683062).

81691366118 is a wasteful number, since it uses less digits than its factorization.

81691366118 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40845683061.

The product of its digits is 373248, while the sum is 50.

The spelling of 81691366118 in words is "eighty-one billion, six hundred ninety-one million, three hundred sixty-six thousand, one hundred eighteen".