81651266081 has 24 divisors (see below), whose sum is σ = 108121915584. Its totient is φ = 60858077280.

The previous prime is 81651266041. The next prime is 81651266087. The reversal of 81651266081 is 18066215618.

It is not a de Polignac number, because 81651266081 - 2¹⁸ = 81651003937 is a prime.

It is a super-2 number, since 2×81651266081² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81651266087) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3280790 + ... + 3305583.

It is an arithmetic number, because the mean of its divisors is an integer number (4505079816).

Almost surely, 2^81651266081 is an apocalyptic number.

It is an amenable number.

81651266081 is a deficient number, since it is larger than the sum of its proper divisors (26470649503).

81651266081 is a wasteful number, since it uses less digits than its factorization.

81651266081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6586421 (or 6586414 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 44.

The spelling of 81651266081 in words is "eighty-one billion, six hundred fifty-one million, two hundred sixty-six thousand, eighty-one".