81523872 has 144 divisors (see below), whose sum is σ = 246486240. Its totient is φ = 25514496.

The previous prime is 81523853. The next prime is 81523873. The reversal of 81523872 is 27832518.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×81523872² = 13292283411744768, which contains 22 as substring.

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 (81523873) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 359023 + ... + 359249.

It is an arithmetic number, because the mean of its divisors is an integer number (1711710).

Almost surely, 2^81523872 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 81523872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123243120).

81523872 is an abundant number, since it is smaller than the sum of its proper divisors (164962368).

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

81523872 is a wasteful number, since it uses less digits than its factorization.

81523872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315 (or 304 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 81523872 is about 9029.0570936283. The cubic root of 81523872 is about 433.6056502670.

The spelling of 81523872 in words is "eighty-one million, five hundred twenty-three thousand, eight hundred seventy-two".