644410666 has 4 divisors (see below), whose sum is σ = 966616002. Its totient is φ = 322205332.

The previous prime is 644410651. The next prime is 644410691. The reversal of 644410666 is 666014446.

It is a happy number.

644410666 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 only one way, i.e., 379665225 + 264745441 = 19485^2 + 16271^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161102665 + ... + 161102668.

Almost surely, 2^644410666 is an apocalyptic number.

644410666 is a deficient number, since it is larger than the sum of its proper divisors (322205336).

644410666 is a wasteful number, since it uses less digits than its factorization.

644410666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322205335.

The product of its (nonzero) digits is 82944, while the sum is 37.

The square root of 644410666 is about 25385.2450451044. The cubic root of 644410666 is about 863.7490313670.

The spelling of 644410666 in words is "six hundred forty-four million, four hundred ten thousand, six hundred sixty-six".