81908645487 has 8 divisors (see below), whose sum is σ = 109393852800. Its totient is φ = 54514600920.

The previous prime is 81908645471. The next prime is 81908645513. The reversal of 81908645487 is 78454680918.

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

It is not a de Polignac number, because 81908645487 - 2⁴ = 81908645471 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81908645487.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (86908645487) 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 7 ways as a sum of consecutive naturals, for example, 22788589 + ... + 22792182.

It is an arithmetic number, because the mean of its divisors is an integer number (13674231600).

Almost surely, 2^81908645487 is an apocalyptic number.

81908645487 is a deficient number, since it is larger than the sum of its proper divisors (27485207313).

81908645487 is a wasteful number, since it uses less digits than its factorization.

81908645487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45581373.

The product of its (nonzero) digits is 15482880, while the sum is 60.

The spelling of 81908645487 in words is "eighty-one billion, nine hundred eight million, six hundred forty-five thousand, four hundred eighty-seven".