81698705909 has 4 divisors (see below), whose sum is σ = 81700359180. Its totient is φ = 81697052640.

The previous prime is 81698705899. The next prime is 81698705951. The reversal of 81698705909 is 90950789618.

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

It can be written as a sum of positive squares in 2 ways, for example, as 22708983025 + 58989722884 = 150695^2 + 242878^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81698705909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81698705969) 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, 750152 + ... + 852129.

It is an arithmetic number, because the mean of its divisors is an integer number (20425089795).

Almost surely, 2^81698705909 is an apocalyptic number.

It is an amenable number.

81698705909 is a deficient number, since it is larger than the sum of its proper divisors (1653271).

81698705909 is a wasteful number, since it uses less digits than its factorization.

81698705909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1653270.

The product of its (nonzero) digits is 9797760, while the sum is 62.

The spelling of 81698705909 in words is "eighty-one billion, six hundred ninety-eight million, seven hundred five thousand, nine hundred nine".