644893920 has 384 divisors, whose sum is σ = 2529999360. Its totient is φ = 152064000.

The previous prime is 644893913. The next prime is 644893933. The reversal of 644893920 is 29398446.

644893920 is nontrivially palindromic in base 14.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1948155 + ... + 1948485.

It is an arithmetic number, because the mean of its divisors is an integer number (6588540).

Almost surely, 2^644893920 is an apocalyptic number.

644893920 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 644893920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1264999680).

644893920 is an abundant number, since it is smaller than the sum of its proper divisors (1885105440).

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

644893920 is a wasteful number, since it uses less digits than its factorization.

644893920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407 (or 393 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 644893920 is about 25394.7616645638. The cubic root of 644893920 is about 863.9648905486.

It can be divided in two parts, 64 and 4893920, that added together give a palindrome (4893984).

The spelling of 644893920 in words is "six hundred forty-four million, eight hundred ninety-three thousand, nine hundred twenty".