81571518 has 48 divisors (see below), whose sum is σ = 205317216. Its totient is φ = 22921920.

The previous prime is 81571517. The next prime is 81571531. The reversal of 81571518 is 81517518.

It is a happy number.

81571518 is a `hidden beast` number, since 81 + 571 + 5 + 1 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81571517) 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 23 ways as a sum of consecutive naturals, for example, 2380 + ... + 12992.

It is an arithmetic number, because the mean of its divisors is an integer number (4277442).

Almost surely, 2^81571518 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81571518, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102658608).

81571518 is an abundant number, since it is smaller than the sum of its proper divisors (123745698).

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

81571518 is a wasteful number, since it uses less digits than its factorization.

81571518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10689 (or 10686 counting only the distinct ones).

The product of its digits is 11200, while the sum is 36.

The square root of 81571518 is about 9031.6951897194. The cubic root of 81571518 is about 433.6901063117.

The spelling of 81571518 in words is "eighty-one million, five hundred seventy-one thousand, five hundred eighteen".