81623520 has 144 divisors (see below), whose sum is σ = 303921072. Its totient is φ = 19783680.

The previous prime is 81623501. The next prime is 81623539. The reversal of 81623520 is 2532618.

81623520 is a `hidden beast` number, since 81 + 62 + 3 + 520 = 666.

It is an interprime number because it is at equal distance from previous prime (81623501) and next prime (81623539).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13264 + ... + 18416.

It is an arithmetic number, because the mean of its divisors is an integer number (2110563).

Almost surely, 2^81623520 is an apocalyptic number.

81623520 is a gapful number since it is divisible by the number (80) 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 81623520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (151960536).

81623520 is an abundant number, since it is smaller than the sum of its proper divisors (222297552).

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

81623520 is a wasteful number, since it uses less digits than its factorization.

81623520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5185 (or 5174 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 81623520 is about 9034.5735925942. The cubic root of 81623520 is about 433.7822461611.

It can be divided in two parts, 816 and 23520, that added together give a square (24336 = 156²).

The spelling of 81623520 in words is "eighty-one million, six hundred twenty-three thousand, five hundred twenty".