644425321 has 4 divisors (see below), whose sum is σ = 644500692. Its totient is φ = 644349952.

The previous prime is 644425291. The next prime is 644425367. The reversal of 644425321 is 123524446.

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 552955225 + 91470096 = 23515^2 + 9564^2 .

It is a cyclic number.

It is not a de Polignac number, because 644425321 - 2⁷ = 644425193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644425381) 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, 22936 + ... + 42601.

It is an arithmetic number, because the mean of its divisors is an integer number (161125173).

Almost surely, 2^644425321 is an apocalyptic number.

It is an amenable number.

644425321 is a deficient number, since it is larger than the sum of its proper divisors (75371).

644425321 is an equidigital number, since it uses as much as digits as its factorization.

644425321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75370.

The product of its digits is 23040, while the sum is 31.

The square root of 644425321 is about 25385.5336953943. The cubic root of 644425321 is about 863.7555790271.

Adding to 644425321 its reverse (123524446), we get a palindrome (767949767).

The spelling of 644425321 in words is "six hundred forty-four million, four hundred twenty-five thousand, three hundred twenty-one".