644620 has 24 divisors (see below), whose sum is σ = 1368864. Its totient is φ = 254976.

The previous prime is 644617. The next prime is 644629. The reversal of 644620 is 26446.

It is a junction number, because it is equal to n+sod(n) for n = 644591 and 644600.

It is not an unprimeable number, because it can be changed into a prime (644629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3244 + ... + 3436.

It is an arithmetic number, because the mean of its divisors is an integer number (57036).

2⁶⁴⁴⁶²⁰ is an apocalyptic number.

It is an amenable number.

644620 is an abundant number, since it is smaller than the sum of its proper divisors (724244).

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

644620 is a wasteful number, since it uses less digits than its factorization.

644620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369 (or 367 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 22.

The square root of 644620 is about 802.8823076890. The cubic root of 644620 is about 86.3842549613.

The spelling of 644620 in words is "six hundred forty-four thousand, six hundred twenty".