643767 has 4 divisors (see below), whose sum is σ = 858360. Its totient is φ = 429176.

The previous prime is 643751. The next prime is 643781. The reversal of 643767 is 767346.

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 643767 - 2⁴ = 643751 is a prime.

It is a d-powerful number, because it can be written as 6² + 4⁸ + 7² + 3¹² + 6⁶ + 7² .

It is a D-number.

643767 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643567) 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, 107292 + ... + 107297.

It is an arithmetic number, because the mean of its divisors is an integer number (214590).

2⁶⁴³⁷⁶⁷ is an apocalyptic number.

643767 is a deficient number, since it is larger than the sum of its proper divisors (214593).

643767 is a wasteful number, since it uses less digits than its factorization.

643767 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214592.

The product of its digits is 21168, while the sum is 33.

The square root of 643767 is about 802.3509207323. The cubic root of 643767 is about 86.3461351929.

The spelling of 643767 in words is "six hundred forty-three thousand, seven hundred sixty-seven".