81813568 has 14 divisors (see below), whose sum is σ = 162348926. Its totient is φ = 40906752.

The previous prime is 81813551. The next prime is 81813577. The reversal of 81813568 is 86531818.

It can be written as a sum of positive squares in only one way, i.e., 75898944 + 5914624 = 8712^2 + 2432^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81813568.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 639105 + ... + 639232.

Almost surely, 2^81813568 is an apocalyptic number.

It is an amenable number.

81813568 is a deficient number, since it is larger than the sum of its proper divisors (80535358).

81813568 is a wasteful number, since it uses less digits than its factorization.

81813568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1278349 (or 1278339 counting only the distinct ones).

The product of its digits is 46080, while the sum is 40.

The square root of 81813568 is about 9045.0852953413. The cubic root of 81813568 is about 434.1186506205.

The spelling of 81813568 in words is "eighty-one million, eight hundred thirteen thousand, five hundred sixty-eight".