644394966 has 16 divisors (see below), whose sum is σ = 1289092800. Its totient is φ = 214747848.

The previous prime is 644394953. The next prime is 644394967. The reversal of 644394966 is 669493446.

It is a super-5 number, since 5×644394966⁵ (a number of 45 digits) contains 55555 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644394967) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22605 + ... + 42423.

It is an arithmetic number, because the mean of its divisors is an integer number (80568300).

Almost surely, 2^644394966 is an apocalyptic number.

644394966 is an abundant number, since it is smaller than the sum of its proper divisors (644697834).

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

644394966 is a wasteful number, since it uses less digits than its factorization.

644394966 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25243.

The product of its digits is 3359232, while the sum is 51.

The square root of 644394966 is about 25384.9358084672. The cubic root of 644394966 is about 863.7420167045.

The spelling of 644394966 in words is "six hundred forty-four million, three hundred ninety-four thousand, nine hundred sixty-six".