644646064 has 40 divisors (see below), whose sum is σ = 1269683120. Its totient is φ = 317011968.

The previous prime is 644646059. The next prime is 644646071. The reversal of 644646064 is 460646446.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 638392 + ... + 639400.

It is an arithmetic number, because the mean of its divisors is an integer number (31742078).

Almost surely, 2^644646064 is an apocalyptic number.

It is an amenable number.

644646064 is a deficient number, since it is larger than the sum of its proper divisors (625037056).

644646064 is a wasteful number, since it uses less digits than its factorization.

644646064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1637 (or 1631 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 40.

The square root of 644646064 is about 25389.8811340266. The cubic root of 644646064 is about 863.8541920731.

The spelling of 644646064 in words is "six hundred forty-four million, six hundred forty-six thousand, sixty-four".