644038321 has 4 divisors (see below), whose sum is σ = 657741312. Its totient is φ = 630335332.

The previous prime is 644038303. The next prime is 644038333. The reversal of 644038321 is 123830446.

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 644038321 - 2¹¹ = 644036273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644038301) 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, 6851425 + ... + 6851518.

It is an arithmetic number, because the mean of its divisors is an integer number (164435328).

Almost surely, 2^644038321 is an apocalyptic number.

It is an amenable number.

644038321 is a deficient number, since it is larger than the sum of its proper divisors (13702991).

644038321 is a wasteful number, since it uses less digits than its factorization.

644038321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13702990.

The product of its (nonzero) digits is 13824, while the sum is 31.

The square root of 644038321 is about 25377.9100991394. The cubic root of 644038321 is about 863.5826392337.

Adding to 644038321 its reverse (123830446), we get a palindrome (767868767).

The spelling of 644038321 in words is "six hundred forty-four million, thirty-eight thousand, three hundred twenty-one".