81539172 has 144 divisors (see below), whose sum is σ = 248032512. Its totient is φ = 22256640.

The previous prime is 81539147. The next prime is 81539173. The reversal of 81539172 is 27193518.

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

It is not an unprimeable number, because it can be changed into a prime (81539173) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 241788 + ... + 242124.

It is an arithmetic number, because the mean of its divisors is an integer number (1722448).

Almost surely, 2^81539172 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 81539172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124016256).

81539172 is an abundant number, since it is smaller than the sum of its proper divisors (166493340).

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

81539172 is a wasteful number, since it uses less digits than its factorization.

81539172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418 (or 413 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 81539172 is about 9029.9043184300. The cubic root of 81539172 is about 433.6327742300.

The spelling of 81539172 in words is "eighty-one million, five hundred thirty-nine thousand, one hundred seventy-two".