644690880 has 448 divisors, whose sum is σ = 2457907200. Its totient is φ = 158699520.

The previous prime is 644690833. The next prime is 644690899. The reversal of 644690880 is 88096446.

It is a happy number.

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

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, 7767319 + ... + 7767401.

It is an arithmetic number, because the mean of its divisors is an integer number (5486400).

Almost surely, 2^644690880 is an apocalyptic number.

644690880 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 644690880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1228953600).

644690880 is an abundant number, since it is smaller than the sum of its proper divisors (1813216320).

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

644690880 is a wasteful number, since it uses less digits than its factorization.

644690880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169 (or 153 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 45.

The square root of 644690880 is about 25390.7636750059. The cubic root of 644690880 is about 863.8742100822.

The spelling of 644690880 in words is "six hundred forty-four million, six hundred ninety thousand, eight hundred eighty".