644394268 has 48 divisors (see below), whose sum is σ = 1337656320. Its totient is φ = 265761216.

The previous prime is 644394263. The next prime is 644394281. The reversal of 644394268 is 862493446.

It is a super-5 number, since 5×644394268⁵ (a number of 45 digits) contains 55555 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644394263) 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, 280621 + ... + 282907.

It is an arithmetic number, because the mean of its divisors is an integer number (27867840).

Almost surely, 2^644394268 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 644394268, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (668828160).

644394268 is an abundant number, since it is smaller than the sum of its proper divisors (693262052).

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

644394268 is a wasteful number, since it uses less digits than its factorization.

644394268 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2674 (or 2672 counting only the distinct ones).

The product of its digits is 995328, while the sum is 46.

The square root of 644394268 is about 25384.9220601522. The cubic root of 644394268 is about 863.7417048398.

The spelling of 644394268 in words is "six hundred forty-four million, three hundred ninety-four thousand, two hundred sixty-eight".