644040000 has 210 divisors, whose sum is σ = 2308081490. Its totient is φ = 171648000.

The previous prime is 644039927. The next prime is 644040011. The reversal of 644040000 is 40446.

It can be written as a sum of positive squares in 5 ways, for example, as 98724096 + 545315904 = 9936^2 + 23352^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 359106 + ... + 360894.

Almost surely, 2^644040000 is an apocalyptic number.

644040000 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 644040000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1154040745).

644040000 is an abundant number, since it is smaller than the sum of its proper divisors (1664041490).

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

644040000 is a wasteful number, since it uses less digits than its factorization.

644040000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1827 (or 1799 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 644040000 is about 25377.9431790679. The cubic root of 644040000 is about 863.5833896828.

Adding to 644040000 its reverse (40446), we get a palindrome (644080446).

The spelling of 644040000 in words is "six hundred forty-four million, forty thousand".