640443 has 4 divisors (see below), whose sum is σ = 853928. Its totient is φ = 426960.

The previous prime is 640421. The next prime is 640457. The reversal of 640443 is 344046.

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

It is not a de Polignac number, because 640443 - 2⁵ = 640411 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640463) 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, 106738 + ... + 106743.

It is an arithmetic number, because the mean of its divisors is an integer number (213482).

2⁶⁴⁰⁴⁴³ is an apocalyptic number.

640443 is a deficient number, since it is larger than the sum of its proper divisors (213485).

640443 is a wasteful number, since it uses less digits than its factorization.

640443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213484.

The product of its (nonzero) digits is 1152, while the sum is 21.

The square root of 640443 is about 800.2768271042. The cubic root of 640443 is about 86.1972666521.

Adding to 640443 its reverse (344046), we get a palindrome (984489).

The spelling of 640443 in words is "six hundred forty thousand, four hundred forty-three".