644345520 has 320 divisors, whose sum is σ = 2487174144. Its totient is φ = 134369280.

The previous prime is 644345503. The next prime is 644345551. The reversal of 644345520 is 25543446.

It is a super-2 number, since 2×644345520² = 830362298288140800, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3559830 + ... + 3560010.

Almost surely, 2^644345520 is an apocalyptic number.

644345520 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 644345520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1243587072).

644345520 is an abundant number, since it is smaller than the sum of its proper divisors (1842828624).

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

644345520 is a wasteful number, since it uses less digits than its factorization.

644345520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 380 (or 374 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 33.

The square root of 644345520 is about 25383.9618657136. The cubic root of 644345520 is about 863.7199237944.

Adding to 644345520 its reverse (25543446), we get a palindrome (669888966).

The spelling of 644345520 in words is "six hundred forty-four million, three hundred forty-five thousand, five hundred twenty".