668440644 has 24 divisors (see below), whose sum is σ = 1561287168. Its totient is φ = 222586080.

The previous prime is 668440637. The next prime is 668440649. The reversal of 668440644 is 446044866.

It is a happy number.

668440644 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×668440644² = 893625789102269472, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 668440596 and 668440605.

It is not an unprimeable number, because it can be changed into a prime (668440649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15972 + ... + 39899.

It is an arithmetic number, because the mean of its divisors is an integer number (65053632).

Almost surely, 2^668440644 is an apocalyptic number.

It is an amenable number.

668440644 is an abundant number, since it is smaller than the sum of its proper divisors (892846524).

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

668440644 is a wasteful number, since it uses less digits than its factorization.

668440644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56875 (or 56873 counting only the distinct ones).

The product of its (nonzero) digits is 442368, while the sum is 42.

The square root of 668440644 is about 25854.2190754236. The cubic root of 668440644 is about 874.3546344337.

The spelling of 668440644 in words is "six hundred sixty-eight million, four hundred forty thousand, six hundred forty-four".