644722000 has 160 divisors (see below), whose sum is σ = 1700453664. Its totient is φ = 235008000.

The previous prime is 644721943. The next prime is 644722019. The reversal of 644722000 is 227446.

644722000 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 16 ways, for example, as 640494864 + 4227136 = 25308^2 + 2056^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3561910 + ... + 3562090.

Almost surely, 2^644722000 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 644722000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (850226832).

644722000 is an abundant number, since it is smaller than the sum of its proper divisors (1055731664).

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

644722000 is a wasteful number, since it uses less digits than its factorization.

644722000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 354 (or 338 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 644722000 is about 25391.3764888791. The cubic root of 644722000 is about 863.8881099390. Note that the first 3 decimals are identical.

Adding to 644722000 its reverse (227446), we get a palindrome (644949446).

The spelling of 644722000 in words is "six hundred forty-four million, seven hundred twenty-two thousand".