644209440 has 192 divisors, whose sum is σ = 2441456640. Its totient is φ = 139484160.

The previous prime is 644209439. The next prime is 644209457. The reversal of 644209440 is 44902446.

It is a super-2 number, since 2×644209440² = 830011605170227200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 58795 + ... + 68885.

It is an arithmetic number, because the mean of its divisors is an integer number (12715920).

Almost surely, 2^644209440 is an apocalyptic number.

644209440 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 644209440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1220728320).

644209440 is an abundant number, since it is smaller than the sum of its proper divisors (1797247200).

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

644209440 is a wasteful number, since it uses less digits than its factorization.

644209440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10135 (or 10127 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 33.

The square root of 644209440 is about 25381.2812915345. The cubic root of 644209440 is about 863.6591162108.

The spelling of 644209440 in words is "six hundred forty-four million, two hundred nine thousand, four hundred forty".