643643 has 16 divisors (see below), whose sum is σ = 865536. Its totient is φ = 462240.

The previous prime is 643639. The next prime is 643649. The reversal of 643643 is 346346.

It is a cyclic number.

It is not a de Polignac number, because 643643 - 2² = 643639 is a prime.

It is a super-2 number, since 2×643643² = 828552622898, which contains 22 as substring.

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (643649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 680 + ... + 1322.

It is an arithmetic number, because the mean of its divisors is an integer number (54096).

2⁶⁴³⁶⁴³ is an apocalyptic number.

643643 is a deficient number, since it is larger than the sum of its proper divisors (221893).

643643 is a wasteful number, since it uses less digits than its factorization.

643643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 674.

The product of its digits is 5184, while the sum is 26.

The square root of 643643 is about 802.2736440891. The cubic root of 643643 is about 86.3405909467.

Adding to 643643 its reverse (346346), we get a palindrome (989989).

The spelling of 643643 in words is "six hundred forty-three thousand, six hundred forty-three".