81441768645 has 24 divisors (see below), whose sum is σ = 142563420792. Its totient is φ = 43005552000.

The previous prime is 81441768643. The next prime is 81441768647. The reversal of 81441768645 is 54686714418.

81441768645 is a `hidden beast` number, since 81 + 441 + 7 + 6 + 86 + 45 = 666.

It is an interprime number because it is at equal distance from previous prime (81441768643) and next prime (81441768647).

It can be written as a sum of positive squares in 4 ways, for example, as 26817665121 + 54624103524 = 163761^2 + 233718^2 .

It is not a de Polignac number, because 81441768645 - 2¹ = 81441768643 is a prime.

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81441768591 and 81441768600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81441768643) 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 23 ways as a sum of consecutive naturals, for example, 8954946 + ... + 8964035.

It is an arithmetic number, because the mean of its divisors is an integer number (5940142533).

Almost surely, 2^81441768645 is an apocalyptic number.

It is an amenable number.

81441768645 is a deficient number, since it is larger than the sum of its proper divisors (61121652147).

81441768645 is a wasteful number, since it uses less digits than its factorization.

81441768645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17919093 (or 17919090 counting only the distinct ones).

The product of its digits is 5160960, while the sum is 54.

The spelling of 81441768645 in words is "eighty-one billion, four hundred forty-one million, seven hundred sixty-eight thousand, six hundred forty-five".