81123331777 has 4 divisors (see below), whose sum is σ = 81300844996. Its totient is φ = 80945818560.

The previous prime is 81123331771. The next prime is 81123331787. The reversal of 81123331777 is 77713332118.

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 31999485456 + 49123846321 = 178884^2 + 221639^2 .

It is a cyclic number.

It is not a de Polignac number, because 81123331777 - 2³¹ = 78975848129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81123331771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 88755924 + ... + 88756837.

It is an arithmetic number, because the mean of its divisors is an integer number (20325211249).

Almost surely, 2^81123331777 is an apocalyptic number.

It is an amenable number.

81123331777 is a deficient number, since it is larger than the sum of its proper divisors (177513219).

81123331777 is a wasteful number, since it uses less digits than its factorization.

81123331777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177513218.

The product of its digits is 148176, while the sum is 43.

The spelling of 81123331777 in words is "eighty-one billion, one hundred twenty-three million, three hundred thirty-one thousand, seven hundred seventy-seven".