644013331 has 8 divisors (see below), whose sum is σ = 695489760. Its totient is φ = 592813632.

The previous prime is 644013323. The next prime is 644013367. The reversal of 644013331 is 133310446.

It is a happy number.

644013331 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 644013331 - 2³ = 644013323 is a prime.

It is a super-2 number, since 2×644013331² = 829506341011431122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644013296 and 644013305.

It is not an unprimeable number, because it can be changed into a prime (644010331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64330 + ... + 73663.

It is an arithmetic number, because the mean of its divisors is an integer number (86936220).

Almost surely, 2^644013331 is an apocalyptic number.

644013331 is a deficient number, since it is larger than the sum of its proper divisors (51476429).

644013331 is a wasteful number, since it uses less digits than its factorization.

644013331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138365.

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 644013331 is about 25377.4177370354. The cubic root of 644013331 is about 863.5714695002.

Adding to 644013331 its reverse (133310446), we get a palindrome (777323777).

The spelling of 644013331 in words is "six hundred forty-four million, thirteen thousand, three hundred thirty-one".