621644 has 24 divisors (see below), whose sum is σ = 1179360. Its totient is φ = 285824.

The previous prime is 621641. The next prime is 621671. The reversal of 621644 is 446126.

It is a happy number.

621644 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is not an unprimeable number, because it can be changed into a prime (621641) 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, 2552 + ... + 2784.

It is an arithmetic number, because the mean of its divisors is an integer number (49140).

2⁶²¹⁶⁴⁴ is an apocalyptic number.

It is an amenable number.

621644 is a deficient number, since it is larger than the sum of its proper divisors (557716).

621644 is a wasteful number, since it uses less digits than its factorization.

621644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289 (or 287 counting only the distinct ones).

The product of its digits is 1152, while the sum is 23.

The square root of 621644 is about 788.4440373292. Note that the first 3 decimals coincide. The cubic root of 621644 is about 85.3454911605.

621644 divided by its sum of digits (23) gives a triangular number (27028 = T₂₃₂).

The spelling of 621644 in words is "six hundred twenty-one thousand, six hundred forty-four".