644643264 has 224 divisors, whose sum is σ = 1952280576. Its totient is φ = 186531840.

The previous prime is 644643173. The next prime is 644643283. The reversal of 644643264 is 462346446.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2327094 + ... + 2327370.

Almost surely, 2^644643264 is an apocalyptic number.

644643264 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644643264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (976140288).

644643264 is an abundant number, since it is smaller than the sum of its proper divisors (1307637312).

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

644643264 is a wasteful number, since it uses less digits than its factorization.

644643264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363 (or 353 counting only the distinct ones).

The product of its digits is 331776, while the sum is 39.

The square root of 644643264 is about 25389.8259938898. The cubic root of 644643264 is about 863.8529413634.

The spelling of 644643264 in words is "six hundred forty-four million, six hundred forty-three thousand, two hundred sixty-four".