81591408 has 40 divisors (see below), whose sum is σ = 234198800. Its totient is φ = 27196992.

The previous prime is 81591383. The next prime is 81591431. The reversal of 81591408 is 80419518.

It is a Harshad number since it is a multiple of its sum of digits (36).

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, 94003 + ... + 94866.

It is an arithmetic number, because the mean of its divisors is an integer number (5854970).

Almost surely, 2^81591408 is an apocalyptic number.

It is an amenable number.

81591408 is an abundant number, since it is smaller than the sum of its proper divisors (152607392).

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

81591408 is a wasteful number, since it uses less digits than its factorization.

81591408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188886 (or 188874 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 81591408 is about 9032.7962447960. The cubic root of 81591408 is about 433.7253530719.

The spelling of 81591408 in words is "eighty-one million, five hundred ninety-one thousand, four hundred eight".