81552640 has 144 divisors (see below), whose sum is σ = 218912400. Its totient is φ = 29073408.

The previous prime is 81552623. The next prime is 81552643. The reversal of 81552640 is 4625518.

It can be written as a sum of positive squares in 8 ways, for example, as 60466176 + 21086464 = 7776^2 + 4592^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81552643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2812146 + ... + 2812174.

It is an arithmetic number, because the mean of its divisors is an integer number (1520225).

Almost surely, 2^81552640 is an apocalyptic number.

81552640 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 81552640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109456200).

81552640 is an abundant number, since it is smaller than the sum of its proper divisors (137359760).

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

81552640 is an equidigital number, since it uses as much as digits as its factorization.

81552640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89 (or 49 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 81552640 is about 9030.6500319744. The cubic root of 81552640 is about 433.6566476009.

The spelling of 81552640 in words is "eighty-one million, five hundred fifty-two thousand, six hundred forty".