643944 has 32 divisors (see below), whose sum is σ = 1840320. Its totient is φ = 183936.

The previous prime is 643927. The next prime is 643949. The reversal of 643944 is 449346.

643944 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a d-powerful number, because it can be written as 6⁶ + 4 + 9⁶ + 3⁵ + 4³ + 4⁸ .

It is not an unprimeable number, because it can be changed into a prime (643949) 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, 1749 + ... + 2084.

It is an arithmetic number, because the mean of its divisors is an integer number (57510).

2⁶⁴³⁹⁴⁴ is an apocalyptic number.

It is an amenable number.

643944 is an abundant number, since it is smaller than the sum of its proper divisors (1196376).

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

643944 is a wasteful number, since it uses less digits than its factorization.

643944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3849 (or 3845 counting only the distinct ones).

The product of its digits is 10368, while the sum is 30.

The square root of 643944 is about 802.4612140160. The cubic root of 643944 is about 86.3540479240.

The spelling of 643944 in words is "six hundred forty-three thousand, nine hundred forty-four".