81508518 has 192 divisors, whose sum is σ = 239715840. Its totient is φ = 20155392.

The previous prime is 81508501. The next prime is 81508519. The reversal of 81508518 is 81580518.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81508519) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 840246 + ... + 840342.

It is an arithmetic number, because the mean of its divisors is an integer number (1248520).

Almost surely, 2^81508518 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81508518, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119857920).

81508518 is an abundant number, since it is smaller than the sum of its proper divisors (158207322).

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

81508518 is a wasteful number, since it uses less digits than its factorization.

81508518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153 (or 141 counting only the distinct ones).

The product of its (nonzero) digits is 12800, while the sum is 36.

The square root of 81508518 is about 9028.2067986949. The cubic root of 81508518 is about 433.5784271605.

The spelling of 81508518 in words is "eighty-one million, five hundred eight thousand, five hundred eighteen".