644887040 has 240 divisors, whose sum is σ = 1851490872. Its totient is φ = 214695936.

The previous prime is 644887031. The next prime is 644887057. The reversal of 644887040 is 40788446.

It can be written as a sum of positive squares in 4 ways, for example, as 558471424 + 86415616 = 23632^2 + 9296^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6648272 + ... + 6648368.

Almost surely, 2^644887040 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 644887040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (925745436).

644887040 is an abundant number, since it is smaller than the sum of its proper divisors (1206603832).

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

644887040 is an equidigital number, since it uses as much as digits as its factorization.

644887040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187 (or 164 counting only the distinct ones).

The product of its (nonzero) digits is 172032, while the sum is 41.

The square root of 644887040 is about 25394.6262031950. The cubic root of 644887040 is about 863.9618181572.

The spelling of 644887040 in words is "six hundred forty-four million, eight hundred eighty-seven thousand, forty".