81374776785 has 24 divisors (see below), whose sum is σ = 141219822120. Its totient is φ = 43347508992.

The previous prime is 81374776781. The next prime is 81374776787. The reversal of 81374776785 is 58767747318.

81374776785 is a `hidden beast` number, since 81 + 3 + 7 + 477 + 6 + 7 + 85 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 5828406336 + 75546370449 = 76344^2 + 274857^2 .

It is not a de Polignac number, because 81374776785 - 2² = 81374776781 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81374776781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1053364 + ... + 1127973.

It is an arithmetic number, because the mean of its divisors is an integer number (5884159255).

Almost surely, 2^81374776785 is an apocalyptic number.

It is an amenable number.

81374776785 is a deficient number, since it is larger than the sum of its proper divisors (59845045335).

81374776785 is a wasteful number, since it uses less digits than its factorization.

81374776785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2182177 (or 2182174 counting only the distinct ones).

The product of its digits is 55319040, while the sum is 63.

The spelling of 81374776785 in words is "eighty-one billion, three hundred seventy-four million, seven hundred seventy-six thousand, seven hundred eighty-five".