644550220 has 48 divisors (see below), whose sum is σ = 1408619520. Its totient is φ = 247536576.

The previous prime is 644550173. The next prime is 644550227. The reversal of 644550220 is 22055446.

It is a super-2 number, since 2×644550220² = 830889972204096800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644550227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44389 + ... + 57091.

It is an arithmetic number, because the mean of its divisors is an integer number (29346240).

Almost surely, 2^644550220 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 644550220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (704309760).

644550220 is an abundant number, since it is smaller than the sum of its proper divisors (764069300).

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

644550220 is a wasteful number, since it uses less digits than its factorization.

644550220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12814 (or 12812 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 28.

The square root of 644550220 is about 25387.9936190318. The cubic root of 644550220 is about 863.8113782204.

It can be divided in two parts, 6445 and 50220, that added together give a palindrome (56665).

The spelling of 644550220 in words is "six hundred forty-four million, five hundred fifty thousand, two hundred twenty".