81106617645 has 24 divisors (see below), whose sum is σ = 140938952856. Its totient is φ = 43147893888.

The previous prime is 81106617601. The next prime is 81106617671. The reversal of 81106617645 is 54671660118.

It can be written as a sum of positive squares in 4 ways, for example, as 4522697001 + 76583920644 = 67251^2 + 276738^2 .

It is not a de Polignac number, because 81106617645 - 2⁹ = 81106617133 is a prime.

It is a super-3 number, since 3×81106617645³ (a number of 34 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81106617645.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 2252122 + ... + 2287851.

It is an arithmetic number, because the mean of its divisors is an integer number (5872456369).

Almost surely, 2^81106617645 is an apocalyptic number.

It is an amenable number.

81106617645 is a deficient number, since it is larger than the sum of its proper divisors (59832335211).

81106617645 is a wasteful number, since it uses less digits than its factorization.

81106617645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4540381 (or 4540378 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 45.

The spelling of 81106617645 in words is "eighty-one billion, one hundred six million, six hundred seventeen thousand, six hundred forty-five".