643813 has 4 divisors (see below), whose sum is σ = 645568. Its totient is φ = 642060.

The previous prime is 643781. The next prime is 643847. The reversal of 643813 is 318346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 643813 - 2⁵ = 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 (643873) 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, 93 + ... + 1138.

It is an arithmetic number, because the mean of its divisors is an integer number (161392).

2⁶⁴³⁸¹³ is an apocalyptic number.

It is an amenable number.

643813 is a deficient number, since it is larger than the sum of its proper divisors (1755).

643813 is a wasteful number, since it uses less digits than its factorization.

643813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1754.

The product of its digits is 1728, while the sum is 25.

The square root of 643813 is about 802.3795859816. The cubic root of 643813 is about 86.3481917484.

The spelling of 643813 in words is "six hundred forty-three thousand, eight hundred thirteen".