644405580 has 144 divisors (see below), whose sum is σ = 2405841984. Its totient is φ = 135959040.

The previous prime is 644405563. The next prime is 644405591. The reversal of 644405580 is 85504446.

644405580 is a `hidden beast` number, since 64 + 4 + 40 + 558 + 0 = 666.

It is a super-3 number, since 3×644405580³ (a number of 27 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3291 + ... + 36050.

It is an arithmetic number, because the mean of its divisors is an integer number (16707236).

Almost surely, 2^644405580 is an apocalyptic number.

644405580 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 644405580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1202920992).

644405580 is an abundant number, since it is smaller than the sum of its proper divisors (1761436404).

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

644405580 is a wasteful number, since it uses less digits than its factorization.

644405580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39376 (or 39371 counting only the distinct ones).

The product of its (nonzero) digits is 76800, while the sum is 36.

The square root of 644405580 is about 25385.1448686038. The cubic root of 644405580 is about 863.7467589863.

The spelling of 644405580 in words is "six hundred forty-four million, four hundred five thousand, five hundred eighty".