643964 has 12 divisors (see below), whose sum is σ = 1134000. Its totient is φ = 319968.

The previous prime is 643961. The next prime is 643969. The reversal of 643964 is 469346.

It is a self number, because there is not a number n which added to its sum of digits gives 643964.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 392 + ... + 1200.

It is an arithmetic number, because the mean of its divisors is an integer number (94500).

2⁶⁴³⁹⁶⁴ is an apocalyptic number.

It is an amenable number.

643964 is a deficient number, since it is larger than the sum of its proper divisors (490036).

643964 is a wasteful number, since it uses less digits than its factorization.

643964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1012 (or 1010 counting only the distinct ones).

The product of its digits is 15552, while the sum is 32.

The square root of 643964 is about 802.4736755807. The cubic root of 643964 is about 86.3549419267.

The spelling of 643964 in words is "six hundred forty-three thousand, nine hundred sixty-four".