644793408 has 336 divisors, whose sum is σ = 2339400960. Its totient is φ = 165445632.

The previous prime is 644793407. The next prime is 644793419. The reversal of 644793408 is 804397446.

It is a tau number, because it is divible by the number of its divisors (336).

It is not an unprimeable number, because it can be changed into a prime (644793407) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1576308 + ... + 1576716.

Almost surely, 2^644793408 is an apocalyptic number.

644793408 is a gapful number since it is divisible by the number (68) 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 644793408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1169700480).

644793408 is an abundant number, since it is smaller than the sum of its proper divisors (1694607552).

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

644793408 is a wasteful number, since it uses less digits than its factorization.

644793408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 474 (or 461 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 45.

The square root of 644793408 is about 25392.7825966356. The cubic root of 644793408 is about 863.9200028814.

The spelling of 644793408 in words is "six hundred forty-four million, seven hundred ninety-three thousand, four hundred eight".