640321 has 4 divisors (see below), whose sum is σ = 698544. Its totient is φ = 582100.

The previous prime is 640307. The next prime is 640333. The reversal of 640321 is 123046.

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 640321 - 2⁷ = 640193 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640295 and 640304.

It is not an unprimeable number, because it can be changed into a prime (640121) 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, 29095 + ... + 29116.

It is an arithmetic number, because the mean of its divisors is an integer number (174636).

2⁶⁴⁰³²¹ is an apocalyptic number.

It is an amenable number.

640321 is a deficient number, since it is larger than the sum of its proper divisors (58223).

640321 is a wasteful number, since it uses less digits than its factorization.

640321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58222.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 640321 is about 800.2005998498. The cubic root of 640321 is about 86.1917929751.

Adding to 640321 its reverse (123046), we get a palindrome (763367).

It can be divided in two parts, 640 and 321, that added together give a square (961 = 31²).

The spelling of 640321 in words is "six hundred forty thousand, three hundred twenty-one".