81768564 has 18 divisors (see below), whose sum is σ = 206692850. Its totient is φ = 27256176.

The previous prime is 81768563. The next prime is 81768581. The reversal of 81768564 is 46586718.

It is a happy number.

81768564 is a `hidden beast` number, since 81 + 7 + 6 + 8 + 564 = 666.

It can be written as a sum of positive squares in only one way, i.e., 50296464 + 31472100 = 7092^2 + 5610^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81768563) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1135639 + ... + 1135710.

Almost surely, 2^81768564 is an apocalyptic number.

It is an amenable number.

81768564 is an abundant number, since it is smaller than the sum of its proper divisors (124924286).

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

81768564 is a wasteful number, since it uses less digits than its factorization.

81768564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2271359 (or 2271354 counting only the distinct ones).

The product of its digits is 322560, while the sum is 45.

The square root of 81768564 is about 9042.5971932847. The cubic root of 81768564 is about 434.0390360380.

The spelling of 81768564 in words is "eighty-one million, seven hundred sixty-eight thousand, five hundred sixty-four".