643728 has 20 divisors (see below), whose sum is σ = 1663088. Its totient is φ = 214560.

The previous prime is 643723. The next prime is 643729. The reversal of 643728 is 827346.

It is a junction number, because it is equal to n+sod(n) for n = 643695 and 643704.

It is not an unprimeable number, because it can be changed into a prime (643723) by changing a digit.

643728 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6658 + ... + 6753.

2⁶⁴³⁷²⁸ is an apocalyptic number.

It is an amenable number.

643728 is an abundant number, since it is smaller than the sum of its proper divisors (1019360).

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

643728 is a wasteful number, since it uses less digits than its factorization.

643728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13422 (or 13416 counting only the distinct ones).

The product of its digits is 8064, while the sum is 30.

The square root of 643728 is about 802.3266167840. The cubic root of 643728 is about 86.3443915148.

It can be divided in two parts, 6 and 43728, that added together give a palindrome (43734).

The spelling of 643728 in words is "six hundred forty-three thousand, seven hundred twenty-eight".