81917408 has 48 divisors (see below), whose sum is σ = 169590960. Its totient is φ = 38900736.

The previous prime is 81917393. The next prime is 81917447. The reversal of 81917408 is 80471918.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 50108 + ... + 51716.

It is an arithmetic number, because the mean of its divisors is an integer number (3533145).

Almost surely, 2^81917408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81917408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84795480).

81917408 is an abundant number, since it is smaller than the sum of its proper divisors (87673552).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81917408 is a wasteful number, since it uses less digits than its factorization.

81917408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1699 (or 1691 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 38.

The square root of 81917408 is about 9050.8236089320. The cubic root of 81917408 is about 434.3022380271.

The spelling of 81917408 in words is "eighty-one million, nine hundred seventeen thousand, four hundred eight".