668492581 has 4 divisors (see below), whose sum is σ = 707815692. Its totient is φ = 629169472.

The previous prime is 668492563. The next prime is 668492593. The reversal of 668492581 is 185294866.

668492581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 442260900 + 226231681 = 21030^2 + 15041^2 .

It is a cyclic number.

It is not a de Polignac number, because 668492581 - 2¹⁹ = 667968293 is a prime.

It is a super-2 number, since 2×668492581² = 893764661704083122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668492501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19661530 + ... + 19661563.

It is an arithmetic number, because the mean of its divisors is an integer number (176953923).

Almost surely, 2^668492581 is an apocalyptic number.

It is an amenable number.

668492581 is a deficient number, since it is larger than the sum of its proper divisors (39323111).

668492581 is a wasteful number, since it uses less digits than its factorization.

668492581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39323110.

The product of its digits is 829440, while the sum is 49.

The square root of 668492581 is about 25855.2234761179. The cubic root of 668492581 is about 874.3772792669.

The spelling of 668492581 in words is "six hundred sixty-eight million, four hundred ninety-two thousand, five hundred eighty-one".