81389191857605 has 8 divisors (see below), whose sum is σ = 99322403623200. Its totient is φ = 64007771223376.

The previous prime is 81389191857583. The next prime is 81389191857641. The reversal of 81389191857605 is 50675819198318.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81389191857605 - 2¹² = 81389191853509 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 137947782515 + ... + 137947783104.

It is an arithmetic number, because the mean of its divisors is an integer number (12415300452900).

Almost surely, 2^{81389191857605} is an apocalyptic number.

It is an amenable number.

81389191857605 is a deficient number, since it is larger than the sum of its proper divisors (17933211765595).

81389191857605 is a wasteful number, since it uses less digits than its factorization.

81389191857605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275895565683.

The product of its (nonzero) digits is 130636800, while the sum is 71.

The spelling of 81389191857605 in words is "eighty-one trillion, three hundred eighty-nine billion, one hundred ninety-one million, eight hundred fifty-seven thousand, six hundred five".