644006464 has 56 divisors (see below), whose sum is σ = 1300276800. Its totient is φ = 316432896.

The previous prime is 644006443. The next prime is 644006471. The reversal of 644006464 is 464600446.

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, 1074837 + ... + 1075435.

Almost surely, 2^644006464 is an apocalyptic number.

644006464 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 644006464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (650138400).

644006464 is an abundant number, since it is smaller than the sum of its proper divisors (656270336).

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

644006464 is a wasteful number, since it uses less digits than its factorization.

644006464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875 (or 865 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 34.

The square root of 644006464 is about 25377.2824392211. The cubic root of 644006464 is about 863.5684001194.

The spelling of 644006464 in words is "six hundred forty-four million, six thousand, four hundred sixty-four".