81205345617 has 32 divisors (see below), whose sum is σ = 120870973440. Its totient is φ = 48072001920.

The previous prime is 81205345607. The next prime is 81205345619. The reversal of 81205345617 is 71654350218.

It is a happy number.

It is not a de Polignac number, because 81205345617 - 2¹⁰ = 81205344593 is a prime.

It is a super-2 number, since 2×81205345617² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81205345619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 728109 + ... + 832197.

It is an arithmetic number, because the mean of its divisors is an integer number (3777217920).

Almost surely, 2^81205345617 is an apocalyptic number.

It is an amenable number.

81205345617 is a deficient number, since it is larger than the sum of its proper divisors (39665627823).

81205345617 is a wasteful number, since it uses less digits than its factorization.

81205345617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104653.

The product of its (nonzero) digits is 201600, while the sum is 42.

The spelling of 81205345617 in words is "eighty-one billion, two hundred five million, three hundred forty-five thousand, six hundred seventeen".