645406321 has 4 divisors (see below), whose sum is σ = 737607232. Its totient is φ = 553205412.

The previous prime is 645406273. The next prime is 645406337. The reversal of 645406321 is 123604546.

645406321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 645406321 - 2¹³ = 645398129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645406351) 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, 46100445 + ... + 46100458.

It is an arithmetic number, because the mean of its divisors is an integer number (184401808).

Almost surely, 2^645406321 is an apocalyptic number.

It is an amenable number.

645406321 is a deficient number, since it is larger than the sum of its proper divisors (92200911).

645406321 is an equidigital number, since it uses as much as digits as its factorization.

645406321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92200910.

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 645406321 is about 25404.8483758514. The cubic root of 645406321 is about 864.1936513125.

The spelling of 645406321 in words is "six hundred forty-five million, four hundred six thousand, three hundred twenty-one".