81538931471881 has 81 divisors (see below), whose sum is σ = 91787596052607. Its totient is φ = 72400943646720.

The previous prime is 81538931471869. The next prime is 81538931471917. The reversal of 81538931471881 is 18817413983518.

The square root of 81538931471881 is 9029891.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 64149030657481 + 17389900814400 = 8009309^2 + 4170120^2 .

It is not a de Polignac number, because 81538931471881 - 2²⁹ = 81538394600969 is a prime.

It is a super-2 number, since 2×81538931471881² (a number of 29 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81538931471801) 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 80 ways as a sum of consecutive naturals, for example, 422481510121 + ... + 422481510313.

Almost surely, 2^{81538931471881} is an apocalyptic number.

81538931471881 is the 9029891-st square number.

81538931471881 is the 4514946-th centered octagonal number.

It is an amenable number.

81538931471881 is a deficient number, since it is larger than the sum of its proper divisors (10248664580726).

81538931471881 is an frugal number, since it uses more digits than its factorization.

81538931471881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 652 (or 326 counting only the distinct ones).

The product of its digits is 46448640, while the sum is 67.

The spelling of 81538931471881 in words is "eighty-one trillion, five hundred thirty-eight billion, nine hundred thirty-one million, four hundred seventy-one thousand, eight hundred eighty-one".