644432880 has 320 divisors, whose sum is σ = 2589834240. Its totient is φ = 128729088.

The previous prime is 644432863. The next prime is 644432927. The reversal of 644432880 is 88234446.

It is a Harshad number since it is a multiple of its sum of digits (39).

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, 414184 + ... + 415736.

It is an arithmetic number, because the mean of its divisors is an integer number (8093232).

Almost surely, 2^644432880 is an apocalyptic number.

644432880 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 644432880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1294917120).

644432880 is an abundant number, since it is smaller than the sum of its proper divisors (1945401360).

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

644432880 is a wasteful number, since it uses less digits than its factorization.

644432880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1608 (or 1602 counting only the distinct ones).

The product of its (nonzero) digits is 147456, while the sum is 39.

The square root of 644432880 is about 25385.6825789656. The cubic root of 644432880 is about 863.7589562495.

The spelling of 644432880 in words is "six hundred forty-four million, four hundred thirty-two thousand, eight hundred eighty".