644384040 has 128 divisors (see below), whose sum is σ = 1979942400. Its totient is φ = 167731200.

The previous prime is 644384033. The next prime is 644384057. The reversal of 644384040 is 40483446.

It is a junction number, because it is equal to n+sod(n) for n = 644383992 and 644384010.

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 31 ways as a sum of consecutive naturals, for example, 957144 + ... + 957816.

It is an arithmetic number, because the mean of its divisors is an integer number (15468300).

Almost surely, 2^644384040 is an apocalyptic number.

644384040 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 644384040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989971200).

644384040 is an abundant number, since it is smaller than the sum of its proper divisors (1335558360).

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

644384040 is a wasteful number, since it uses less digits than its factorization.

644384040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 867 (or 863 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 33.

The square root of 644384040 is about 25384.7206011805. The cubic root of 644384040 is about 863.7371349684.

The spelling of 644384040 in words is "six hundred forty-four million, three hundred eighty-four thousand, forty".