81547320977 has 4 divisors (see below), whose sum is σ = 81721940976. Its totient is φ = 81372700980.

The previous prime is 81547320973. The next prime is 81547321039. The reversal of 81547320977 is 77902374518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 77902374518 = 2 ⋅38951187259.

It is a cyclic number.

It is not a de Polignac number, because 81547320977 - 2² = 81547320973 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81547320973) 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, 87309299 + ... + 87310232.

It is an arithmetic number, because the mean of its divisors is an integer number (20430485244).

Almost surely, 2^81547320977 is an apocalyptic number.

It is an amenable number.

81547320977 is a deficient number, since it is larger than the sum of its proper divisors (174619999).

81547320977 is a wasteful number, since it uses less digits than its factorization.

81547320977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174619998.

The product of its (nonzero) digits is 2963520, while the sum is 53.

The spelling of 81547320977 in words is "eighty-one billion, five hundred forty-seven million, three hundred twenty thousand, nine hundred seventy-seven".