81689518727 has 4 divisors (see below), whose sum is σ = 82673729880. Its totient is φ = 80705307576.

The previous prime is 81689518723. The next prime is 81689518789. The reversal of 81689518727 is 72781598618.

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

It is a cyclic number.

It is not a de Polignac number, because 81689518727 - 2² = 81689518723 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81689518727.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689518721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 492105452 + ... + 492105617.

It is an arithmetic number, because the mean of its divisors is an integer number (20668432470).

Almost surely, 2^81689518727 is an apocalyptic number.

81689518727 is a deficient number, since it is larger than the sum of its proper divisors (984211153).

81689518727 is an equidigital number, since it uses as much as digits as its factorization.

81689518727 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 984211152.

The product of its digits is 13547520, while the sum is 62.

The spelling of 81689518727 in words is "eighty-one billion, six hundred eighty-nine million, five hundred eighteen thousand, seven hundred twenty-seven".