81920340197 has 4 divisors (see below), whose sum is σ = 86739183756. Its totient is φ = 77101496640.

The previous prime is 81920340143. The next prime is 81920340211. The reversal of 81920340197 is 79104302918.

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 33974231041 + 47946109156 = 184321^2 + 218966^2 .

It is a cyclic number.

It is not a de Polignac number, because 81920340197 - 2¹⁴ = 81920323813 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 (81920340497) 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 3 ways as a sum of consecutive naturals, for example, 2409421754 + ... + 2409421787.

It is an arithmetic number, because the mean of its divisors is an integer number (21684795939).

Almost surely, 2^81920340197 is an apocalyptic number.

It is an amenable number.

81920340197 is a deficient number, since it is larger than the sum of its proper divisors (4818843559).

81920340197 is a wasteful number, since it uses less digits than its factorization.

81920340197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4818843558.

The product of its (nonzero) digits is 108864, while the sum is 44.

The spelling of 81920340197 in words is "eighty-one billion, nine hundred twenty million, three hundred forty thousand, one hundred ninety-seven".