640120321 has 4 divisors (see below), whose sum is σ = 640390212. Its totient is φ = 639850432.

The previous prime is 640120237. The next prime is 640120339. The reversal of 640120321 is 123021046.

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 199120321 + 441000000 = 14111^2 + 21000^2 .

It is a cyclic number.

It is not a de Polignac number, because 640120321 - 2¹¹ = 640118273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640120361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131356 + ... + 136141.

It is an arithmetic number, because the mean of its divisors is an integer number (160097553).

Almost surely, 2^640120321 is an apocalyptic number.

It is an amenable number.

640120321 is a deficient number, since it is larger than the sum of its proper divisors (269891).

640120321 is a wasteful number, since it uses less digits than its factorization.

640120321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269890.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 640120321 is about 25300.5992221528. The cubic root of 640120321 is about 861.8278775738.

Adding to 640120321 its reverse (123021046), we get a palindrome (763141367).

The spelling of 640120321 in words is "six hundred forty million, one hundred twenty thousand, three hundred twenty-one".