644956338 has 64 divisors (see below), whose sum is σ = 1420231680. Its totient is φ = 194052672.

The previous prime is 644956321. The next prime is 644956339. The reversal of 644956338 is 833659446.

It is not an unprimeable number, because it can be changed into a prime (644956339) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 872373 + ... + 873111.

It is an arithmetic number, because the mean of its divisors is an integer number (22191120).

Almost surely, 2^644956338 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644956338, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (710115840).

644956338 is an abundant number, since it is smaller than the sum of its proper divisors (775275342).

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

644956338 is a wasteful number, since it uses less digits than its factorization.

644956338 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 991.

The product of its digits is 1866240, while the sum is 48.

The square root of 644956338 is about 25395.9905890674. The cubic root of 644956338 is about 863.9927634639.

The spelling of 644956338 in words is "six hundred forty-four million, nine hundred fifty-six thousand, three hundred thirty-eight".