644564620 has 36 divisors (see below), whose sum is σ = 1574581680. Its totient is φ = 220993248.

The previous prime is 644564579. The next prime is 644564621. The reversal of 644564620 is 26465446.

It is a self number, because there is not a number n which added to its sum of digits gives 644564620.

It is not an unprimeable number, because it can be changed into a prime (644564621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 327880 + ... + 329839.

It is an arithmetic number, because the mean of its divisors is an integer number (43738380).

Almost surely, 2^644564620 is an apocalyptic number.

It is an amenable number.

644564620 is an abundant number, since it is smaller than the sum of its proper divisors (930017060).

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

644564620 is a wasteful number, since it uses less digits than its factorization.

644564620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 657742 (or 657733 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 37.

The square root of 644564620 is about 25388.2772160696. The cubic root of 644564620 is about 863.8178110221.

The spelling of 644564620 in words is "six hundred forty-four million, five hundred sixty-four thousand, six hundred twenty".