643667 has 4 divisors (see below), whose sum is σ = 658680. Its totient is φ = 628656.

The previous prime is 643661. The next prime is 643681. The reversal of 643667 is 766346.

643667 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643667 - 2⁴ = 643651 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643667.

It is not an unprimeable number, because it can be changed into a prime (643661) 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, 7442 + ... + 7527.

It is an arithmetic number, because the mean of its divisors is an integer number (164670).

2⁶⁴³⁶⁶⁷ is an apocalyptic number.

643667 is a deficient number, since it is larger than the sum of its proper divisors (15013).

643667 is a wasteful number, since it uses less digits than its factorization.

643667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15012.

The product of its digits is 18144, while the sum is 32.

The square root of 643667 is about 802.2886014397. The cubic root of 643667 is about 86.3416640822.

The spelling of 643667 in words is "six hundred forty-three thousand, six hundred sixty-seven".