81122771921 has 4 divisors (see below), whose sum is σ = 81135276144. Its totient is φ = 81110267700.

The previous prime is 81122771911. The next prime is 81122771923. The reversal of 81122771921 is 12917722118.

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 81122771921 - 2¹⁸ = 81122509777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81122771923) 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, 6242375 + ... + 6255356.

It is an arithmetic number, because the mean of its divisors is an integer number (20283819036).

Almost surely, 2^81122771921 is an apocalyptic number.

It is an amenable number.

81122771921 is a deficient number, since it is larger than the sum of its proper divisors (12504223).

81122771921 is a wasteful number, since it uses less digits than its factorization.

81122771921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12504222.

The product of its digits is 28224, while the sum is 41.

The spelling of 81122771921 in words is "eighty-one billion, one hundred twenty-two million, seven hundred seventy-one thousand, nine hundred twenty-one".