644005620 has 48 divisors (see below), whose sum is σ = 2003574720. Its totient is φ = 171734688.

The previous prime is 644005619. The next prime is 644005631. The reversal of 644005620 is 26500446.

It is a happy number.

644005620 is a `hidden beast` number, since 64 + 40 + 0 + 562 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 595762 + ... + 596841.

It is an arithmetic number, because the mean of its divisors is an integer number (41741140).

Almost surely, 2^644005620 is an apocalyptic number.

644005620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644005620 is an abundant number, since it is smaller than the sum of its proper divisors (1359569100).

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

644005620 is a wasteful number, since it uses less digits than its factorization.

644005620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1192621 (or 1192613 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 644005620 is about 25377.2658101695. The cubic root of 644005620 is about 863.5680228706.

The spelling of 644005620 in words is "six hundred forty-four million, five thousand, six hundred twenty".