644336401 has 4 divisors (see below), whose sum is σ = 644409892. Its totient is φ = 644262912.

The previous prime is 644336393. The next prime is 644336437. The reversal of 644336401 is 104633446.

It is a happy number.

644336401 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 brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 493906176 + 150430225 = 22224^2 + 12265^2 .

It is a cyclic number.

It is not a de Polignac number, because 644336401 - 2³ = 644336393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644336101) 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, 21480 + ... + 41833.

It is an arithmetic number, because the mean of its divisors is an integer number (161102473).

Almost surely, 2^644336401 is an apocalyptic number.

It is an amenable number.

644336401 is a deficient number, since it is larger than the sum of its proper divisors (73491).

644336401 is a wasteful number, since it uses less digits than its factorization.

644336401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73490.

The product of its (nonzero) digits is 20736, while the sum is 31.

The square root of 644336401 is about 25383.7822437871. The cubic root of 644336401 is about 863.7158492211.

Adding to 644336401 its reverse (104633446), we get a palindrome (748969847).

The spelling of 644336401 in words is "six hundred forty-four million, three hundred thirty-six thousand, four hundred one".