640136321 has 8 divisors (see below), whose sum is σ = 715363488. Its totient is φ = 567748000.

The previous prime is 640136317. The next prime is 640136323. The reversal of 640136321 is 123631046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640136321 - 2² = 640136317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640136323) 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 7 ways as a sum of consecutive naturals, for example, 709235 + ... + 710136.

It is an arithmetic number, because the mean of its divisors is an integer number (89420436).

Almost surely, 2^640136321 is an apocalyptic number.

It is an amenable number.

640136321 is a deficient number, since it is larger than the sum of its proper divisors (75227167).

640136321 is a wasteful number, since it uses less digits than its factorization.

640136321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1419423.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 640136321 is about 25300.9154182215. The cubic root of 640136321 is about 861.8350580630.

Adding to 640136321 its reverse (123631046), we get a palindrome (763767367).

The spelling of 640136321 in words is "six hundred forty million, one hundred thirty-six thousand, three hundred twenty-one".