644664404 has 6 divisors (see below), whose sum is σ = 1128162714. Its totient is φ = 322332200.

The previous prime is 644664379. The next prime is 644664421. The reversal of 644664404 is 404466446.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 641608900 + 3055504 = 25330^2 + 1748^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80583047 + ... + 80583054.

It is an arithmetic number, because the mean of its divisors is an integer number (188027119).

Almost surely, 2^644664404 is an apocalyptic number.

It is an amenable number.

644664404 is a deficient number, since it is larger than the sum of its proper divisors (483498310).

644664404 is a wasteful number, since it uses less digits than its factorization.

644664404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161166105 (or 161166103 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 38.

The square root of 644664404 is about 25390.2422989620. The cubic root of 644664404 is about 863.8623841320.

The spelling of 644664404 in words is "six hundred forty-four million, six hundred sixty-four thousand, four hundred four".