644380536 has 64 divisors (see below), whose sum is σ = 1653955200. Its totient is φ = 209130368.

The previous prime is 644380523. The next prime is 644380537. The reversal of 644380536 is 635083446.

It is a junction number, because it is equal to n+sod(n) for n = 644380494 and 644380503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644380537) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 149386 + ... + 153638.

It is an arithmetic number, because the mean of its divisors is an integer number (25843050).

Almost surely, 2^644380536 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644380536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (826977600).

644380536 is an abundant number, since it is smaller than the sum of its proper divisors (1009574664).

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

644380536 is a wasteful number, since it uses less digits than its factorization.

644380536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4428 (or 4424 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 39.

The square root of 644380536 is about 25384.6515831910. The cubic root of 644380536 is about 863.7355693697.

The spelling of 644380536 in words is "six hundred forty-four million, three hundred eighty thousand, five hundred thirty-six".