81381255075 has 72 divisors (see below), whose sum is σ = 150940361520. Its totient is φ = 41864659200.

The previous prime is 81381255013. The next prime is 81381255077. The reversal of 81381255075 is 57055218318.

81381255075 is a `hidden beast` number, since 8 + 13 + 8 + 12 + 550 + 75 = 666.

It is a Cunningham number, because it is equal to 285274²-1.

It is not a de Polignac number, because 81381255075 - 2²⁰ = 81380206499 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81381255075.

It is not an unprimeable number, because it can be changed into a prime (81381255077) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 7126120 + ... + 7137530.

It is an arithmetic number, because the mean of its divisors is an integer number (2096393910).

Almost surely, 2^81381255075 is an apocalyptic number.

81381255075 is a deficient number, since it is larger than the sum of its proper divisors (69559106445).

81381255075 is a wasteful number, since it uses less digits than its factorization.

81381255075 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12549 (or 12541 counting only the distinct ones).

The product of its (nonzero) digits is 336000, while the sum is 45.

The spelling of 81381255075 in words is "eighty-one billion, three hundred eighty-one million, two hundred fifty-five thousand, seventy-five".