81959913161 has 12 divisors (see below), whose sum is σ = 95363741700. Its totient is φ = 70234688160.

The previous prime is 81959913149. The next prime is 81959913241. The reversal of 81959913161 is 16131995918.

It can be written as a sum of positive squares in 2 ways, for example, as 73736143936 + 8223769225 = 271544^2 + 90685^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81959913161 is a prime.

It is a super-2 number, since 2×81959913161² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81959913131) 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, 12515 + ... + 405063.

It is an arithmetic number, because the mean of its divisors is an integer number (7946978475).

Almost surely, 2^81959913161 is an apocalyptic number.

It is an amenable number.

81959913161 is a deficient number, since it is larger than the sum of its proper divisors (13403828539).

81959913161 is a wasteful number, since it uses less digits than its factorization.

81959913161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396824 (or 396817 counting only the distinct ones).

The product of its digits is 524880, while the sum is 53.

The spelling of 81959913161 in words is "eighty-one billion, nine hundred fifty-nine million, nine hundred thirteen thousand, one hundred sixty-one".