81259995681 has 6 divisors (see below), whose sum is σ = 117375549330. Its totient is φ = 54173330448.

The previous prime is 81259995667. The next prime is 81259995689. The reversal of 81259995681 is 18659995218.

81259995681 is a `hidden beast` number, since 8 + 12 + 59 + 9 + 9 + 568 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 81028469025 + 231526656 = 284655^2 + 15216^2 .

It is not a de Polignac number, because 81259995681 - 2³¹ = 79112512033 is a prime.

It is a super-2 number, since 2×81259995681² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81259995689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4514444196 + ... + 4514444213.

It is an arithmetic number, because the mean of its divisors is an integer number (19562591555).

Almost surely, 2^81259995681 is an apocalyptic number.

It is an amenable number.

81259995681 is a deficient number, since it is larger than the sum of its proper divisors (36115553649).

81259995681 is a wasteful number, since it uses less digits than its factorization.

81259995681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9028888415 (or 9028888412 counting only the distinct ones).

The product of its digits is 13996800, while the sum is 63.

The spelling of 81259995681 in words is "eighty-one billion, two hundred fifty-nine million, nine hundred ninety-five thousand, six hundred eighty-one".