81972745997 has 4 divisors (see below), whose sum is σ = 81973690656. Its totient is φ = 81971801340.

The previous prime is 81972745963. The next prime is 81972746021. The reversal of 81972745997 is 79954727918.

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.

It is a cyclic number.

It is not a de Polignac number, because 81972745997 - 2³² = 77677778701 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 (81972748997) 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, 327329 + ... + 520662.

It is an arithmetic number, because the mean of its divisors is an integer number (20493422664).

Almost surely, 2^81972745997 is an apocalyptic number.

It is an amenable number.

81972745997 is a deficient number, since it is larger than the sum of its proper divisors (944659).

81972745997 is an equidigital number, since it uses as much as digits as its factorization.

81972745997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 944658.

The product of its digits is 80015040, while the sum is 68.

The spelling of 81972745997 in words is "eighty-one billion, nine hundred seventy-two million, seven hundred forty-five thousand, nine hundred ninety-seven".