81625824 has 144 divisors (see below), whose sum is σ = 279377280. Its totient is φ = 22083840.

The previous prime is 81625813. The next prime is 81625829. The reversal of 81625824 is 42852618.

81625824 is a `hidden beast` number, since 8 + 1 + 625 + 8 + 24 = 666.

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

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81625829) 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, 37239 + ... + 39369.

It is an arithmetic number, because the mean of its divisors is an integer number (1940120).

Almost surely, 2^81625824 is an apocalyptic number.

81625824 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81625824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139688640).

81625824 is an abundant number, since it is smaller than the sum of its proper divisors (197751456).

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

81625824 is a wasteful number, since it uses less digits than its factorization.

81625824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2173 (or 2162 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 81625824 is about 9034.7011018628. The cubic root of 81625824 is about 433.7863276027.

The spelling of 81625824 in words is "eighty-one million, six hundred twenty-five thousand, eight hundred twenty-four".