81591606 has 24 divisors (see below), whose sum is σ = 177872760. Its totient is φ = 27029376.

The previous prime is 81591593. The next prime is 81591607. The reversal of 81591606 is 60619518.

81591606 is a `hidden beast` number, since 8 + 1 + 591 + 60 + 6 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10971 + ... + 16838.

It is an arithmetic number, because the mean of its divisors is an integer number (7411365).

Almost surely, 2^81591606 is an apocalyptic number.

81591606 is an abundant number, since it is smaller than the sum of its proper divisors (96281154).

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

81591606 is a wasteful number, since it uses less digits than its factorization.

81591606 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27980 (or 27977 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 81591606 is about 9032.8072048505. The cubic root of 81591606 is about 433.7257039158.

The spelling of 81591606 in words is "eighty-one million, five hundred ninety-one thousand, six hundred six".