644667408 has 240 divisors, whose sum is σ = 2293888896. Its totient is φ = 164136960.

The previous prime is 644667407. The next prime is 644667427. The reversal of 644667408 is 804766446.

It is not an unprimeable number, because it can be changed into a prime (644667407) 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, 587116 + ... + 588212.

Almost surely, 2^644667408 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 644667408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1146944448).

644667408 is an abundant number, since it is smaller than the sum of its proper divisors (1649221488).

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

644667408 is a wasteful number, since it uses less digits than its factorization.

644667408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1182 (or 1173 counting only the distinct ones).

The product of its (nonzero) digits is 774144, while the sum is 45.

The square root of 644667408 is about 25390.3014554770. The cubic root of 644667408 is about 863.8637259353.

The spelling of 644667408 in words is "six hundred forty-four million, six hundred sixty-seven thousand, four hundred eight".