81506600 has 72 divisors (see below), whose sum is σ = 220468590. Its totient is φ = 27941760.

The previous prime is 81506587. The next prime is 81506609. The reversal of 81506600 is 660518.

It can be written as a sum of positive squares in 3 ways, for example, as 78039556 + 3467044 = 8834^2 + 1862^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81506600.

It is not an unprimeable number, because it can be changed into a prime (81506609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 5642 + ... + 13958.

Almost surely, 2^81506600 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 81506600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110234295).

81506600 is an abundant number, since it is smaller than the sum of its proper divisors (138961990).

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

81506600 is a wasteful number, since it uses less digits than its factorization.

81506600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8347 (or 8331 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 81506600 is about 9028.1005754256. The cubic root of 81506600 is about 433.5750262483.

The spelling of 81506600 in words is "eighty-one million, five hundred six thousand, six hundred".