643789 has 4 divisors (see below), whose sum is σ = 650524. Its totient is φ = 637056.

The previous prime is 643781. The next prime is 643847. The reversal of 643789 is 987346.

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

It can be written as a sum of positive squares in 2 ways, for example, as 110889 + 532900 = 333^2 + 730^2 .

It is a cyclic number.

It is not a de Polignac number, because 643789 - 2³ = 643781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643781) 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 3 ways as a sum of consecutive naturals, for example, 3222 + ... + 3415.

It is an arithmetic number, because the mean of its divisors is an integer number (162631).

2⁶⁴³⁷⁸⁹ is an apocalyptic number.

It is an amenable number.

643789 is a deficient number, since it is larger than the sum of its proper divisors (6735).

643789 is an equidigital number, since it uses as much as digits as its factorization.

643789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6734.

The product of its digits is 36288, while the sum is 37.

The square root of 643789 is about 802.3646303271. The cubic root of 643789 is about 86.3471187751.

The spelling of 643789 in words is "six hundred forty-three thousand, seven hundred eighty-nine".