81528304132781 has 6 divisors (see below), whose sum is σ = 89613755782446. Its totient is φ = 74116640120600.

The previous prime is 81528304132777. The next prime is 81528304132811. The reversal of 81528304132781 is 18723140382518.

It can be written as a sum of positive squares in only one way, i.e., 48583757742025 + 32944546390756 = 6970205^2 + 5739734^2 .

It is not a de Polignac number, because 81528304132781 - 2² = 81528304132777 is a prime.

It is a super-2 number, since 2×81528304132781² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81528304132721) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 336893818610 + ... + 336893818851.

It is an arithmetic number, because the mean of its divisors is an integer number (14935625963741).

Almost surely, 2^{81528304132781} is an apocalyptic number.

It is an amenable number.

81528304132781 is a deficient number, since it is larger than the sum of its proper divisors (8085451649665).

81528304132781 is a wasteful number, since it uses less digits than its factorization.

81528304132781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 673787637483 (or 673787637472 counting only the distinct ones).

The product of its (nonzero) digits is 2580480, while the sum is 53.

The spelling of 81528304132781 in words is "eighty-one trillion, five hundred twenty-eight billion, three hundred four million, one hundred thirty-two thousand, seven hundred eighty-one".