644436000 has 672 divisors, whose sum is σ = 2706985008. Its totient is φ = 149299200.

The previous prime is 644435971. The next prime is 644436007. The reversal of 644436000 is 634446.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 11209104 + 633226896 = 3348^2 + 25164^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (644436007) by changing a digit.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 37907992 + ... + 37908008.

Almost surely, 2^644436000 is an apocalyptic number.

644436000 is a gapful number since it is divisible by the number (60) 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 644436000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1353492504).

644436000 is an abundant number, since it is smaller than the sum of its proper divisors (2062549008).

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

644436000 is a wasteful number, since it uses less digits than its factorization.

644436000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73 (or 40 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 644436000 is about 25385.7440308532. The cubic root of 644436000 is about 863.7603502006.

The spelling of 644436000 in words is "six hundred forty-four million, four hundred thirty-six thousand".