81471018681 has 12 divisors (see below), whose sum is σ = 126732695908. Its totient is φ = 50136011424.

The previous prime is 81471018667. The next prime is 81471018703. The reversal of 81471018681 is 18681017418.

It can be written as a sum of positive squares in 2 ways, for example, as 6444878400 + 75026140281 = 80280^2 + 273909^2 .

It is not a de Polignac number, because 81471018681 - 2⁶ = 81471018617 is a prime.

It is a super-2 number, since 2×81471018681² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81471018611) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 348166630 + ... + 348166863.

Almost surely, 2^81471018681 is an apocalyptic number.

It is an amenable number.

81471018681 is a deficient number, since it is larger than the sum of its proper divisors (45261677227).

81471018681 is a wasteful number, since it uses less digits than its factorization.

81471018681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 696333512 (or 696333509 counting only the distinct ones).

The product of its (nonzero) digits is 86016, while the sum is 45.

The spelling of 81471018681 in words is "eighty-one billion, four hundred seventy-one million, eighteen thousand, six hundred eighty-one".