644007000 has 384 divisors, whose sum is σ = 2524616640. Its totient is φ = 135475200.

The previous prime is 644006963. The next prime is 644007029. The reversal of 644007000 is 700446.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1910832 + ... + 1911168.

Almost surely, 2^644007000 is an apocalyptic number.

644007000 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 644007000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1262308320).

644007000 is an abundant number, since it is smaller than the sum of its proper divisors (1880609640).

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

644007000 is a wasteful number, since it uses less digits than its factorization.

644007000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 367 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 644007000 is about 25377.2929998454. The cubic root of 644007000 is about 863.5686396991.

Adding to 644007000 its reverse (700446), we get a palindrome (644707446).

The spelling of 644007000 in words is "six hundred forty-four million, seven thousand".