643764 has 24 divisors (see below), whose sum is σ = 1639008. Its totient is φ = 195040.

The previous prime is 643751. The next prime is 643781. The reversal of 643764 is 467346.

643764 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

643764 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is an upside-down number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2307 + ... + 2570.

It is an arithmetic number, because the mean of its divisors is an integer number (68292).

2⁶⁴³⁷⁶⁴ is an apocalyptic number.

It is an amenable number.

643764 is an abundant number, since it is smaller than the sum of its proper divisors (995244).

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

643764 is a wasteful number, since it uses less digits than its factorization.

643764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4895 (or 4893 counting only the distinct ones).

The product of its digits is 12096, while the sum is 30.

The square root of 643764 is about 802.3490512240. The cubic root of 643764 is about 86.3460010663.

It can be divided in two parts, 64 and 3764, that added together give a triangular number (3828 = T₈₇).

The spelling of 643764 in words is "six hundred forty-three thousand, seven hundred sixty-four".