81961977797 has 4 divisors (see below), whose sum is σ = 93670831776. Its totient is φ = 70253123820.

The previous prime is 81961977737. The next prime is 81961977827. The reversal of 81961977797 is 79777916918.

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 81961977797 - 2²⁰ = 81960929221 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 81961977797.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81961977737) 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, 5854426979 + ... + 5854426992.

It is an arithmetic number, because the mean of its divisors is an integer number (23417707944).

Almost surely, 2^81961977797 is an apocalyptic number.

It is an amenable number.

81961977797 is a deficient number, since it is larger than the sum of its proper divisors (11708853979).

81961977797 is a wasteful number, since it uses less digits than its factorization.

81961977797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11708853978.

The product of its digits is 84015792, while the sum is 71.

The spelling of 81961977797 in words is "eighty-one billion, nine hundred sixty-one million, nine hundred seventy-seven thousand, seven hundred ninety-seven".